We built a fully onchain orderbook for two of Ethereum's oldest tokens (2016 Unicorn experiment)

Some backstory

In February 2016 — less than a year after Ethereum launched — Alex Van de Sande (avsa) from the Ethereum Foundation deployed an experimental contract called Unicorns (0x89205A3A). It was one of the very first token contracts on Ethereum, predating the ERC-20 standard.

A month later, he created Unicorn Meat (0xED6aC8de) — another experimental token — along with the Grinder Association DAO, one of the earliest DAOs on Ethereum. The Grinder let you exchange Unicorns for Unicorn Meat, effectively the first onchain token swap.

These were demo contracts for the Mist browser. They were never meant to become "real" tokens, but they've survived for 10 years now — still on mainnet, still functional, still held in wallets.

The problem

Because these tokens predate ERC-20 (they have 0 decimal places, non-standard transfer functions), they don't work well with modern DEXes. Uniswap V3's fee math rounds to 0 for 0-decimal tokens. AMM pooling is essentially broken for them.

Wrapped versions exist (w🦄 and w🍖 are standard ERC-20s), but the 0-decimal problem persists.

What we built

Unicorn Market — a fully onchain orderbook contract, purpose-built for these tokens:

• No backend, no matching engine, no admin keys — pure smart contract
• Escrowed limit orders — maker's tokens held in contract until filled or cancelled
• Partial fills — take any portion of an order
• Deterministic rounding — uses OpenZeppelin's Math.mulDiv with ceiling rounding so makers never get shorted
• All state onchain, all settlement via events

Verified contract: 0xA352B50A91C648c97F7aC0a80D686D297b62693E

Trade interface: unicornmeateth.com/market

Source: github.com/cartoonitunes/unicorn-market

Why this matters (beyond the meme)

There are hundreds of pre-ERC-20 and non-standard tokens stuck on Ethereum mainnet with no good trading infrastructure. AMMs assume standard decimals and transfer behavior. A simple, auditable orderbook contract is arguably the right primitive for these edge cases.

If you hold any legacy Ethereum tokens from 2015-2017, you probably know the pain of trying to trade them on modern infra.

Technical details

• Reentrancy-guarded, CEI pattern throughout

Happy to answer questions about the contract design or the history of these tokens.