Designing a card that lives on four chains
From surface finish to chip firmware — the physical object that is xo.
A payment card is the only piece of your bank you can hold. Most issuers treat it as a printed rectangle; we treated it as consumer electronics. The xo titanium weighs 25 grams, is milled — not stamped — from grade-5 titanium, and carries exactly two features on its face: a deeply engraved XO monogram and a gold EMV contact plate. No number, no name, no expiry. Everything sensitive lives in the app, where it can be rotated in one tap.
Subtraction as luxury
Early prototypes had the usual furniture — embossed PAN, hologram, signature strip. Every element we removed made the object feel more expensive, because the eye reads restraint as confidence. The final face has a surface roughness spec (Ra 0.4) tighter than most laptop chassis, and the engraving is cut to a depth you can feel with a fingernail. The metal is the brand.
The four tiers share one geometry and differ only in material truth: aluminium, brushed gold PVD, matte ceramic-black, and raw titanium. ISO 7810 ID-1 dimensions — 85.60 by 53.98 millimeters — because a beautiful object that fails at a card reader is a sculpture, not a product.
The chip is a wallet
The interesting engineering is invisible. The secure element runs firmware that attests to the xo app through the phone's Secure Enclave on every provisioning, and the same balance that funds a Visa authorization can settle from USDC on Base or Solana, USDT on Tron, or fiat — the router decides at authorization time, and cashback returns in USDC regardless. Four blockchains and five fiat rails, hiding behind a single tap that has to work in 300 milliseconds at a bodega card reader.
That is the design brief in one sentence: make the most complicated settlement stack in consumer finance feel like a very nice piece of metal.