The .ac extension is intended for Saint Helena, Ascension and Tristan da Cunha, it’s also interesting that the region has .sh. AC primarily for Ascension Island and .SH primarily for Saint Helena.
There are not many reported .ac domain name sales. BookName.com smashed the record for reported .ac sale with Pay.ac selling for $20,000. It’s the first five figure .ac domain name sale reported. Blockchain.ac sold for only $1,000 in 2019.