Ah, I wasn’t aware of this, but it makes a lot of sense! It even looks like it could be a ligature of “eac”, and it’s very natural to imagine a cursive each bei

Ah, I wasn’t aware of this, but it makes a lot of sense! It even looks like it could be a ligature of “eac”, and it’s very natural to imagine a cursive each being abbreviated first to @h and eventually to just @ by a busy clerk.