Many of the ETH asic's have migrated to ETC, but how many estimated machines were produced? If we took the hash rate of ETH before the merge and compared it to ETC before the merge and get the difference, we would get somewhat of an idea of how much hash power migrated. And from there possibly get a rough estimate of how many ETH asic's there are, because we must assume GPU mining is totally dead on ETC because of ASIC's.
First we'll look at the hash rate before merge and after on ETC. Around Sept 1, hash rate was 42TH. It creeped up 50-70TH a week before the merge. The day of the merge ETC hash rate went up to 303TH, which dwindled down to 160TH as of today.
Using the latest ETH ASIC miner as a base:
2022 July: Miner: Antminer E9 will give out 2,400 MH/s (2.4gh) = 25 GPU's
2020 Dec: Innosilicon A10pro 6G 720MH (.7gh)
Let's assume the optimal average TH of all ETH asic's is .001TH (1gh) = 1 asic Using the lowest possible average TH of all ETH asic's is .0003TH (300gh) = 1 asic
Optimal: 160TH / .001TH = 160,000 ASIC miners
Lowest Possible: 160TH / .0003TH = 533,333 ASIC miners