Trade like a desk, not a chatroom.

01Why a handshake protocol

The historical bottleneck of in-person trading isn't price — it's memory. Screenshots get lost. Group-chat messages drift out of order. "He said the BGS was a 9.5" turns into a he-said dispute the next week.

Handshake Protocol is a two-sided ledger: both phones independently write the same receipt at the same timestamp. Neither party can edit it after the handshake closes. If a disagreement comes up later, both Vaults show the same record — including which exact slabs and which exact serials changed hands.

02What's on the receipt

Every receipt is non-PII by default — handles, not legal names; GPS buckets, not coordinates. The fields written to both Vaults:

• Cards moved. Identifier, set, grade, and serial when present.
• Cash leg. If either side added cash, the amount and direction.
• Spread. Realized-comp value of each side at the moment of signing, plus the net.
• Timestamp. Both phones' local clocks, plus a server-side reconciliation timestamp.
• Location bucket. Coarse GPS hash — "downtown LA convention center", not your exact aisle.
• Counterparty handle. The other side's SYND handle, plus their trade reputation snapshot.

03Vendor mode in 60 seconds

If you're a small vendor, Trade Desk runs as your point-of-sale. Open Vendor mode, tap the QR icon, and the buyer scans the storefront QR to load your live catalogue. You don't need an e-commerce site — your inventory is already in the Vault, and Vendor mode just exposes the public-facing subset.

Sales close the same way trades do: both sides sign, the receipt writes, and the sold cards leave your inventory automatically. If you take cash and want a printed receipt, Vendor mode can email or export the PDF on the spot.

04Reputation, the lightweight kind

Every signed handshake increments your counterparty's trade count. Disputes lower the SIG (signature) percentage. Nothing else is collected — there's no public profile, no rating-stars hellscape, no comment threads. The goal is to give you a one-glance sanity check on whether the person across the table has actually traded before, not to build another social network.