'80's Groove tubes GT12ay7 - what is it?

[rockybottom16]

I found a GT12ay7 in my box of junk that I bought in the early 80's. Anybody know what this is or who made it? I put it in my 5e3 clone and initial impressions are that it sounds pretty nice. Maybe not quite as loud as the EH12ay7 that came with the kit, but nice tone. Anybody?