From an Ethereum Wiki to the World's ERC-20 Standard

In the chaotic early days of Ethereum, there was no standard for tokens. Developers were creating incompatible contracts, leading to ecosystem fragmentation.

Recognizing this, Vitalik Buterin initiated the Standardized_Contract_APIs repository on GitHub. This public workspace became the cited foundation for what would eventually become ERC-20. The process was collaborative; developers like Caktux and Simon de la Rouviere (Simondlr) and many others contributed ideas and code, debating function names like disapprove versus unapprove.

On September 6, 2015, Vitalik Buterin committed the Solidity version of currency.sol, which served as the initial code template used in discussions and cited in the Final ERC-20 Standard. Just two days later, on September 8, 2015, developer 'rfikki' deployed a modified version of this contract to the mainnet. This deployment became a live implementation of some of the earliest code examples by which currency.sol was used to later formalize the official EIP-20 proposal.