# Pieces registered by lot (anchored mode) For high-volume QR brands: each lot is recorded on the blockchain in one single entry, and a piece's token is created only when its buyer claims it. Source: https://docs.sealtrust.io/en/pieces-ancrees/ --- By the end of this page, you will know what anchored mode changes for your pieces, what its record proves and does not prove, when a piece gets its own token, and how a third party checks a piece's proof without trusting us. ## The principle By default, every minted piece immediately gets its own token on the Base blockchain. This is the "one piece, one token" mode. In anchored mode, the pieces of a lot are created in SealTrust, with their serial number and their signed QR code, exactly as today. The whole lot is then recorded on the blockchain in one single entry: a Merkle root, a fingerprint that sums up every piece of the lot. Each piece keeps its own proof that it belongs to that root. A piece gets its token only on the day it first moves: when its buyer claims it, or when your brand transfers it. A piece that is never claimed never gets a token. This mode suits a brand that prints QR codes in large numbers to fight the grey market: it needs a provable serial number for each piece, not one token per piece from the factory. ## Who turns it on The SealTrust team, at your request. The setting applies to the whole brand. It never changes while one of the brand's mints is in progress, and every change is written to the audit log. Nothing changes for pieces already created: a piece that has its token keeps it, and a piece recorded through its lot gets its token on its first claim, whatever the brand's mode is at that time. Anchored mode covers QR-only pieces. An NFC chip is encoded with its token: an NFC lot is still minted piece by piece. ## Minting a lot The gesture is the same: "Mint the batch (grouped)" on the batch page. There is nothing else to do. The pieces exist from the click. QR codes, the archive to print and purchase codes are prepared as usual. The lot's record is sent right away, in one single transaction. If it cannot be sent at once (network unavailable, fees too high), it is sent again automatically within the hour: the lot page shows "Waiting to be recorded on the blockchain. It happens automatically within 1 hour". Once the transaction is confirmed, the batch page shows "Recorded on the blockchain on …", with the link to the transaction and the gas used. If the blockchain refuses the record, or if the transaction stays without confirmation for an hour, it is sent again automatically at the next hourly pass. Nothing is sent blindly: when the root is already recorded, the transaction that recorded it is kept. Until then, the piece's public page shows "Registered, record refused" or "Registered, record pending", and nothing is presented as proven. A mint in anchored mode covers one lot at a time. Every piece must belong to the lot, and to your brand. ## What the record proves It proves that your brand registered this serial number, in this lot, no later than the date of the block that carries the transaction, and that the recorded fields have not changed since. On its own, it does not prove that the object a person holds carries this number, nor who owns it. Ownership starts with the claim, with the token. The piece's public page, the one its QR code opens, shows "Registered and anchored" once the transaction is confirmed, with the date, the link to the transaction and the proof. Before confirmation, it shows "Registered, record pending". ## When a piece gets its token On its first claim, the token is created then handed to the buyer, in the same request. Your brand's claim rules apply as for any piece: purchase code required, in-store activation, time window. A second claim is refused as today. On the first transfer made by your brand, the token is created then transferred, once the transfer's confirmation code has been entered: a request abandoned before that code creates nothing. The token of a piece registered by its lot is created by a single signature. A brand that signs through a multisignature vault (Safe) therefore cannot switch to anchored mode, and a vault cannot be activated while pieces of the brand are waiting for their token. The grey-market check applies to the piece, not to its token: it applies from the moment the piece is created. ## Checking a piece's proof The proof is read without an API key, with the serial number printed on the QR code: ```bash curl https://api.sealtrust.io/v1/verify/unit-anchor/K4QNAFCHDETK ``` The response gives `status` (`recorded` once the transaction is confirmed, `pending` before, `failed` if the blockchain refused it), the recorded fields `leaf_fields`, the leaf `leaf`, its position `leaf_index`, the proof `proof`, the root `merkle_root`, the lot identifier on the contract `onchain_batch_id`, the transaction and its link `explorer_url`, the date `recorded_at`, and `token_minted`. The same information comes in the `unit_anchor` field of `GET /v1/resolve/{identifier}`. To redo the check yourself: 1. recompute the leaf from `leaf_fields`: ```text keccak256(abi.encode( bytes32 keccak256("sealtrust.unit-anchor.v1"), string serial, string brand_code, uint256 product_model_id, string lot_code, bytes32 uid_hash, uint64 created_at_unix )) ``` 2. climb the proof: at each step, hash the current value with the next value of `proof`, the smaller of the two first (OpenZeppelin's `MerkleProof` convention). The result must be `merkle_root`; 3. read `anchoredRootByBatch(onchain_batch_id)` on the contract: the value must be the same root. `onchain_root_matches` gives the result of that read made by our servers, for information. `uid_hash` is also the fingerprint of the token the piece will get: its token number is that fingerprint read as a number. The token created later is therefore the token of the recorded piece. A piece that was not created in anchored mode answers 404: it has its own token, and its proof is elsewhere ([trust and proofs](/en/confiance-et-preuves/)). ## What to remember - Anchored mode records a whole lot in one single transaction; each piece keeps its proof. - Nothing more to click: the record leaves with the mint, and is sent again on its own within the hour if needed. - A piece gets its token on its first claim or its first transfer, never before. - The record proves the registration of the number and its date, not the possession of the object.