November 2, 2019 Proof of Work nonce data is used to identify the presence of ASIC miners.

CoinMetrics uses the distribution of valid pseudorandom nonce values to identify the presence and evolution of ASIC miners across a variety of Proof of Work metrics. A nonce value is found by hashing a block header using a cryptographic function (such as SHA-256); valid blocks have a nonce value lower than a predetermined target. Since any nonce can produce a winning hash and confirm a block, it is expected that nonces be distributed randomly. In a variety of networks, most clearly Monero, nonce distributions are non-uniform and frequently change around the time that ASICs are deployed.