Metal seed backup comparison: which one should you choose?

In this review, we compare plates, cards and capsules to help you choose a metal seed backup. We also cover kits for storing Shamir backup shares and the OneKey Lite NFC card, explaining how many words each option holds and which tools you need to record them.

The material, recording method and fasteners all affect whether a phrase will remain readable after the backup is damaged. We distinguish manufacturers’ claims from the results of Jameson Lopp’s independent stress tests so you can compare products using verified information.

When to move your seed phrase to metal and when paper is enough

A seed phrase is a set of words used to recover a wallet; its length depends on the standard and wallet settings. Common lengths are 12, 20 or 24 words. A paper copy can last for years in a dry drawer, but fire or flooding can destroy it. In Ukraine, fires caused by attacks are another risk to consider when choosing how and where to store a backup. A metal backup helps protect the record from physical damage, although its durability depends on the material and construction.

We recommend a metal seed backup if losing the funds in your wallet would have a substantial impact on you, or if the phrase is stored somewhere you cannot regularly check its condition, such as your parents’ home, a safe-deposit box or another city. If you are just starting to use cryptocurrency and hold a small amount, a paper record in a dry, secure place can be a starting point while you prioritize getting a hardware wallet.

How Jameson Lopp tests metal backups

Jameson Lopp, co-founder of the bitcoin multisig storage service Casa, maintains an open database of metal backup stress tests. He buys the devices, records a test phrase on them and checks whether it can still be read after three tests. His methodology describes the following conditions:

• Heat. The device is exposed to a propane torch flame at 1093 °C for 10 minutes or until it fails, then submerged in a bucket of water to simulate rapid cooling during firefighting.
• Corrosion. The device is left in a 16% hydrochloric acid solution for 12 hours or until the reaction stops.
• Crushing. The device is deformed using a 20-ton hydraulic press, after which Lopp checks whether the record is still readable.

These tests compare the durability of backups under a consistent procedure, but they do not reproduce every condition of a real fire or building collapse. In particular, the torch’s flame temperature does not mean the metal stays at that temperature throughout the test. Lopp describes the acid test as an extreme challenge that reveals how well the material and surface markings hold up. The grades from A to F are his own assessments; he explicitly states that these are not laboratory certifications.

Lopp’s current database includes five models from this review: Cryptotag Zeus, Odin and Thor, Cryptosteel Capsule and Keystone Tablet Punch. For the others, the table below indicates that they have not been tested in this particular database; we do not treat manufacturers’ claims as independent ratings.

A metal’s melting point alone does not determine whether a phrase will survive. A manufacturer’s stated temperature limit does not show how the screws, tiles and markings will behave under heat, even though they also affect the record’s survival. For example, Keystone Tablet Plus, which is not included in this review, uses the same 304 steel as Tablet Punch and has the same stated range of 1399–1455 °C. Yet in Lopp’s test, its slots expanded under heat and the letter tiles fell out, which he classified as catastrophic data loss.

Three recording methods and their weak points

Most models are made from stainless steel or titanium, but they record the phrase in different ways. The recording method affects whether the information stays in place and can still be read after the backup is damaged.

Letter tiles: SafePal Cypher, Cryptosteel Capsule and Seed12

Pre-made metal letter tiles are inserted into slots or threaded onto a rod. This requires no hammer, and mistakes are easy to correct by moving a tile. Because the letters depend on fasteners, damage to the assembly can cause the record to be lost. In Lopp’s tests, Cryptosteel Cassette and Keystone Tablet Plus lost some letters after heating, while the crushing test caused almost all the tiles to fall out of the Cassette. Capsule survived the heat test, but its tube bent so far under the press that the cap could no longer be unscrewed.

Stamped letters: Stamp Seed, Cryptotag Thor, Seedor and SecuX Xseed steel cards

Each letter is struck into the metal with an individual stamp and a hammer. The characters remain on the plate itself and do not depend on fasteners holding separate tiles, which gives this design an advantage under heat and deformation. Producing clear impressions takes practice and firm strikes with consistent force. The work is noisy, which is why Cryptotag kits include earplugs. An incorrect impression cannot be erased, and whether you can correct it depends on the layout of the particular backup. If a practice piece is included, use it before recording your phrase.

Center-punch marks: Keystone Tablet Punch, Trezor Keep Metal, OneKey KeyTag and Cryptotag

An automatic center punch is a spring-loaded tool that makes an indentation in metal with a single press. It marks a position on the layout: beside a letter, as on Trezor, or in a numbered cell, as on Zeus and KeyTag. You can record the phrase without a hammer, but you need to check the position of every mark against the manufacturer’s instructions.

To read the phrase, you must be able to distinguish the punched marks and interpret them using the layout. The indentations may remain readable after heat exposure even if the surface markings are damaged. On Keystone Tablet Punch, acid removed most of the lines and numbers and left surface damage that was difficult to distinguish from the punch marks. Zeus also lost part of its template; Lopp says the data can be recovered, although doing so takes some effort.

Metal seed backup comparison: the models

The product cards show current prices and available options. We cover OneKey Lite separately at the end of this section.

Keystone Tablet Punch: center-punch recording on three plates

Keystone Tablet Punch consists of three plates made from 304 steel: the front plate holds words 1–6, the double-sided middle plate holds words 7–18, and the back plate holds words 19–24. It supports phrases of 12, 18 and 24 words, recording only the first four letters of each word. That is enough to identify a word uniquely in the English BIP39 list of 2048 words; three-letter words are recorded in full. An automatic center punch is included, so no hammer is needed.

In Lopp’s tests, Tablet Punch received an overall B: A for heat and crushing, D for corrosion. The marks remained readable after heating, although many unrelated marks appeared on the plates. Acid destroyed much of the layout, making recovery significantly harder. The plates also developed substantial rust after being left outdoors for several weeks following the crushing test.

The test results make it an affordable option for protecting a record against high temperatures. Because its corrosion resistance is weaker, however, we recommend storing it in a dry room and avoiding damp basements and garages.

SecuX Xseed: aluminum and steel cards in one kit

The Xseed kit contains two aluminum cards and two steel cards. The aluminum cards are marked with the included engraving pen, while the steel cards require letter stamps and a hammer, which must be purchased separately. A protective cover and two seals are also included.

The aluminum and steel cards differ in their heat resistance. SecuX specifies 1454 °C for the steel, while the aluminum cards melt at around 660 °C. The latter can be used for practice or as a water-resistant copy, but we do not recommend relying on them for protection against fire. Xseed is not listed in Lopp’s test database.

Cryptosteel Seed12 Security Kit: a capsule for 12 words

Seed12 Security Kit is a capsule for one 12-word BIP39 phrase, recorded using the first four letters of each word. The kit includes the capsule, a rod, four cotter pins, more than 12 separators, more than 310 double-sided letter tiles and three numbered seals. It can also hold passwords up to 64 characters long; Seed24 is a separate model for 24-word phrases.

Cotter pins secure the tiles at both ends of the rod, and the assembled record can be stored inside the protective capsule. This differs from the older Cryptosteel Capsule design, so Lopp’s rating for Capsule does not apply to Seed12.

SafePal Cypher: letter tiles beneath screw-fastened covers

SafePal Cypher has two plates made from 304 steel, each holding 12 words. Covers hold the tiles in place, with five screws securing each cover. Each word has four cells for its first four letters; the device holds one 24-word phrase or two 12-word phrases. For a three-letter word, the fourth cell is filled with a tile turned blank-side up.

SafePal warns that the kit may not always include enough tiles for a particular letter. Check that you have every letter you need before assembly; the manufacturer allows the tiles to be rotated for the pairs b/q, d/p and n/u. Do not omit a required letter: the record must clearly identify the word you need to recover. Cypher can be filled in without a hammer, but it has no independent Lopp rating.

OneKey KeyTag: compact titanium plates

KeyTag is made from TC4 titanium alloy: each plate measures 36 × 33.5 mm, is 3 mm thick and weighs 14 g. Each row represents one word, and the numbers in the marked cells add up to that word’s number in OneKey’s table. To avoid calculation errors, you can use the ready-made BIP39-Dotmap. The kit includes two plates, an automatic center punch and instructions with the table; each plate holds 24 words.

KeyTag is considerably smaller than most plates in this review, but you need OneKey’s table to recover the words from the marks. Keep a copy of the table and instructions separate from the phrase itself so you do not depend on the manufacturer’s website remaining available. KeyTag has not been tested in Lopp’s database.

Cryptotag Loki: a titanium plate supporting BIP39 and SLIP39

Loki is a titanium plate 3 mm thick that holds 24 words, with 12 on each side. It supports BIP39 and SLIP39, including Trezor’s 20-word backups. The kit includes an automatic center punch, a pencil for preliminary marking, two covers that conceal the record from view, and earplugs.

Lopp’s database has no results for Loki. Although it uses the same material as Zeus and Odin, their grades cannot automatically be applied to Loki: its construction and layout are different.

Trezor Keep Metal: the 24-word version

The 24-word Keep Metal is a backup made from AISI 304 stainless steel inside a protective capsule. It has a black coating and a layout for recording words. Each word has four rows of the alphabet A–Z: you mark the first letter in the first row, the second in the second row, and so on. First mark the intended letters with the included marker, which leaves erasable marks. Once you have checked them, use the center punch to make indentations. The kit also includes seals.

A misplaced punch mark cannot be erased, so Trezor recommends running Check backup in Trezor Suite before using the center punch and checking all preliminary marks. If the wrong letter is punched into Keep Metal, the manufacturer recommends starting again on a new backup.

Trezor reports a 1000-hour neutral salt spray test using ISO 9227. This tests corrosion resistance rather than establishing a specific temperature the backup can withstand in a fire. Keep Metal has not been tested in Lopp’s database.

Cryptosteel Capsule Solo and Duo: one or two capsules

Cryptosteel Capsule is a steel tube containing letter tiles threaded onto a rod. Solo includes one capsule; Duo includes two, and the kits contain more than 800 letter and symbol tiles. A capsule can hold 12 full words or a shortened phrase of 20 or 24 words using the first four letters of each word. This section covers the older Capsule design; the newer Seed24 uses different fasteners, so the older test results do not apply to it.

In Lopp’s test, Capsule received an overall A−: A for heat, A for corrosion and B for crushing. It could be opened by hand after heating, and acid did not enter the capsule during the corrosion test.

The 20-ton press bent the tube so severely that the cap, which is rigidly attached to the rod, could no longer be unscrewed. Lopp suggested that accessing the record would require cutting open the tube and carefully removing the rod without scattering the tiles; he did not cut it open himself. He also noted that reading the phrase was awkward because the tiles were tightly packed and awkwardly oriented on the rod.

Cryptotag Zeus: recording word numbers on titanium

Zeus consists of two titanium plates, each 6 mm thick, on which you use a center punch to mark word numbers from the manufacturer’s table. The starter kit’s plates hold one 24-word phrase or two 12-word phrases, and a center punch is included. The Expansion Kit adds another two plates for 24 words but does not include tools.

Zeus received an A in all three of Lopp’s tests. He specifically praised its fasteners: the sliding clips that hold the plates together can be removed with an ordinary flat-head screwdriver even after deformation. Acid partially removed the etched template, making parts of the record harder to read.

Seedor Safe Starter Set: words and numbers on individual discs

Seedor Safe contains a capsule and discs made from AISI 316L stainless steel. Each disc is stamped with a word of up to eight letters and its position in the phrase. The kit includes at least 28 discs, letter and number stamps, a holder, a steel base, a 500 g hammer and four seals with serial numbers. The manufacturer states support for BIP39, SLIP39 and 25-word Monero phrases.

The numbering helps you restore the correct word order even if the discs are scattered. If you create a new wallet, you can replace the used discs while keeping the capsule and tools. Seedor Safe is not listed in Lopp’s test database.

Stamp Seed Deluxe Titanium: a kit for stamping 24 words

Stamp Seed Deluxe Titanium includes a solid titanium plate 2 mm thick for 24 words, with letters stamped into it using a hammer. The kit contains A–Z stamps and digits 0–8; the six stamp is turned upside down to make a nine. It also includes a hammer with a brass striking face, a steel anvil, a holder that secures the plate, a titanium practice piece and a case.

The manufacturer claims resistance up to 1650 °C and publishes its own tests, but this model has no rating in Lopp’s database. The solid plate has no tiles or fasteners whose failure could release the letters, although readability also depends on the quality of the impressions. Practice on the included sample to learn how much force to use and where to strike before recording the phrase.

Cryptotag Odin: a backup for Shamir shares

Odin is a set of titanium hexagonal rods for SLIP39 backups. Each rod holds one 20-word share; Odin 3, Odin 5 and Odin 7 differ in the number of rods included. For each word, you find its number in the SLIP39 list and mark it on the rod with a center punch. In a “2 of 3” scheme, any two shares can recover the wallet: losing one does not lock you out, and one share alone is not enough for someone else to recover it.

In Lopp’s tests, Odin received an A in all three categories. After heating, the template could be read at the right angle; after acid exposure, all markings remained legible; and the 20-ton press only slightly bent the rod. Lopp also recommends resting the rod on the included anvil when working near an edge: without support, it can rotate and the center punch can slip, injuring your hand.

Cryptotag Thor: two titanium plates for 48 words

Thor contains two titanium plates 6 mm thick, holding 48 words in total: two 24-word phrases or four 12-word phrases. For English BIP39 words, the first four letters of each word are enough. The starter kit includes a hammer, A–Z stamps, an anvil with a rubber base, a stamp holder and earplugs. The Expansion Kit adds another two plates for 48 words without tools.

Lopp tested Thor before Zeus and gave it an A in every test. Heating only slightly darkened the plates, while the acid and crushing tests left the entire record intact. During stamping, a hard strike caused one plate to jam in the holder; to release it, Lopp turned the holder upside down and struck it against concrete several times.

OneKey Lite: an encrypted backup on an NFC card

OneKey Lite is a plastic NFC card with a chip that stores an encrypted backup of one seed phrase. It works with the OneKey mobile app and the OneKey Pro hardware wallet. A PIN protects access to the record, and 10 consecutive incorrect attempts erase the data. The card needs no battery, and a new backup overwrites the previous one.

OneKey Lite can serve as a compact additional copy for OneKey users. However, the manufacturer provides no fire-resistance data, so a metal seed backup is a better choice for protection against fire.

Comparing materials, recording methods and test results

Recording methods and word capacity

Materials and test results

Which metal seed backup should you choose?

If you are buying your first metal seed backup and want to keep costs down, consider Keystone Tablet Punch. It survived independent heat testing, but its weaker corrosion resistance calls for a dry storage location.

For one 24-word phrase, if independent test results are your main priority, consider Cryptotag Zeus. It received an A in every Lopp test, and its screw-free fasteners could still be opened after deformation.

For several phrases, consider the 48-word Cryptotag Thor or Zeus with an expansion kit. The Zeus starter kit is enough for two wallets with 12-word phrases.

Cryptotag Odin is designed for a backup split into 20-word SLIP39 shares; store each share in a separate secure location according to your chosen scheme. For a single 20-word phrase, the appropriate Keep Metal version or Cryptotag Loki will work. If you have a 33-word SLIP39 share, one Odin rod or one Loki does not have enough capacity.

If you want to fill in a backup without a hammer, consider Keystone Tablet Punch, Trezor Keep Metal, OneKey KeyTag or Cryptotag Loki, which use a center punch. SafePal Cypher and Cryptosteel Seed12 are alternatives with pre-made tiles. Among these models, Keystone Tablet Punch has been tested in Lopp’s database.

For a 25-word Monero phrase, consider Seedor Safe: the manufacturer states support for this format.

We do not recommend the aluminum SecuX Xseed cards or OneKey Lite for protection against fire. The aluminum cards have a much lower melting point than steel backups, while OneKey Lite’s documentation provides no verified fire-resistance data.

How to store a metal seed backup

• Check the seed phrase before recording it on metal. Depending on your wallet, run Check backup in Trezor Suite or the Recovery Check app on your Ledger. Check the spelling, word order and preliminary marks before punching or stamping the metal.
• Do not photograph a completed backup: if your phone’s photo library syncs with cloud storage, the image containing the phrase will be uploaded to that service’s servers.
• Store the passphrase separately from the seed phrase. Anyone who finds both records together will have all the information needed to access that wallet.
• Use seals if the product is designed for them. If a seal has been broken without your knowledge, treat the phrase as potentially compromised and move the funds to a wallet with a new phrase. Covers such as Cryptotag Loki Privacy Covers primarily conceal the record from view and do not replace a secure storage location.
• Inspect the backup at least once a year: check for rust and make sure every character is readable. Steel models stored in a basement or garage need more frequent inspections.
• If you keep a paper copy, store it in a different location. Damage to or loss of one backup will then leave you with the other copy.

If you do not see the expected balance after recovering a wallet, use our guide to checking addresses, passphrases and app settings.