Hello everyone,
I’d like to introduce a project I’ve been working on for the past several months:
Proof of Sats, physical collectible cards containing rare sats identified through the Ordinals protocol.

Before getting into the project itself, I’d like to make one short clarification about rare sats.
PreambleI’m fully aware that satoshi numbering is not a native property of Bitcoin Core. It is an off-chain convention that makes it possible to identify and track individual satoshis by applying deterministic rules to transaction history.
Everyone is free to consider that convention interesting, useless, or completely arbitrary.
But the idea itself predates Ordinals by many years. As early as 2012, several developers were discussing here on Bitcointalk the possibility of assigning a unique serial number to individual satoshis:
https://bitcointalk.org/index.php?topic=117224Casascius notably suggested numbering satoshis continuously from the Genesis block:
https://bitcointalk.org/index.php?topic=117224.msg1260610#msg1260610That is exactly the integer notation used by Ordinals today.
I also find it interesting that some of the conventions later adopted by Ordinals were independently proposed here roughly ten years apart:
https://bitcointalk.org/index.php?topic=5430668.0Another important clarification: unlike inscriptions, a rare sat does not add any data to the blockchain. Its classification is derived from data that is already there.
I have always been a collector myself, and I find the idea fascinating that certain satoshis can be collected because of their position, provenance, or history.
That is where Proof of Sats came from.
Proof of SatsThe idea is simple:
to materialize particular satoshis as physical collectible cards.
The first series is limited to 100 cards. Each card contains a satoshi originating from the oldest bitcoin still in circulation: a bitcoin mined by Satoshi Nakamoto in Block 9 on January 9, 2009.
Strictly speaking, the Block 9 sats in Series 1 are
exotic sats, not rare sats under Rodarmor’s rarity classification. The rarity tiers (uncommon, rare, epic, legendary and mythic) are defined by a satoshi’s position within Bitcoin’s block structure. His original thread is itself titled
Ordinals: Rare and exotic sats.
At a time when everyone seems to be trying to tokenize physical objects, I liked the idea of doing the opposite: giving physical form to an asset that exists only digitally.
How a card is madeEach card has a unique guilloché design, inspired in particular by patterns used on banknotes and certificates of authenticity.
The pattern is generated deterministically from the satoshi number using SHA-256.
So each card is as unique as the sat it contains.
The card also displays the information needed to identify and verify the satoshi. Everything can be independently checked against the blockchain using a compatible Ordinals indexer.
The private keyThis is obviously the most sensitive part of the project.
The private keys are generated on a dedicated machine that is kept
completely offline. I bought it specifically for this purpose and physically removed its Wi-Fi card.
The keys are printed using a wired printer with no Wi-Fi capability. I then delete the files containing the private keys.
The cards themselves are printed by a professional
without the private keys. I add the keys myself afterwards, under a custom VOID security seal made specifically for the project.

I want to be completely transparent about one point:
you have no way of verifying that I actually destroyed the private keys, and I have no cryptographic way of proving it.
Casascius acknowledged exactly the same trust assumption with his physical bitcoins:
“When I create a physical bitcoin, one must trust that I am not keeping the private key.”
My cards have the same limitation.
However, an important part of the system does not depend on my word.
The satoshi contained in the card is not intended to be moved.
The owner can therefore check at any time that the UTXO associated with the card remains unspent, without opening the card or revealing the private key.
If I ever moved the satoshi contained in a card I had sold, the transaction would be public, permanent and immediately verifiable.
The sats used in this series also have a relatively limited market value compared with the potential value of the project itself. Sweeping the cards would make little economic sense and would publicly destroy the credibility of the entire project.
One issue with the first production runI also want to document a mistake present on some cards from this first production run.
In some UTXOs, the rare sat is in the last position rather than the first.
Because the cards are already sealed and the private keys have been destroyed, I obviously cannot reorganize those UTXOs anymore.
This has no consequence as long as the sat remains in the card.
However, if someone eventually opens the card and sweeps the private key using a wallet that is not Ordinals-aware, the rare sat could end up being allocated to the transaction fee.
I will therefore provide a procedure and a small tool that will make it possible to move the satoshi safely regardless of its position within the UTXO.
Recovery is therefore still possible, but it naturally requires opening the seal and destroying the integrity of the card as a sealed collectible.
In my view,
the sat is not meant to leave the card. But the owner should obviously always remain able to recover it.
What comes nextI have currently produced two series of 100 cards each, numbered from 1 to 100, as well as a small Genesis series of 22 cards, numbered from 0 to 21.
Genesis #0 is a special one. It contains an Uncommon sat (the first sat of a block) mined only a few minutes before my son was born in July 2010.
It was the first card I ever made, and I gave it to him.

I would now like to explore other categories of sats: Uncommon sats, Alpha sats, palindromes, Pizza sats, and other sats connected to Bitcoin history.
I also want to offer custom cards containing satoshis with a more personal meaning: a sat mined on the day of a birth, a wedding, or another significant event, for example.
If we are going to materialize pieces of Bitcoin, I also like the idea of materializing its almost watch-like precision.
I’m currently building an online store where people will eventually be able to choose a card number and buy it in BTC or fiat.
Thanks for reading, I’m particularly interested in hearing what you think about the concept.