Moose,

I've got a bit of conjecture about your AT** mark. As you know, it's in the area of the frame reserved for the manufacturer's mark and model number, and I think that's exactly what it is. Imagine that the "A" is actually a "D" with a minus sign part way across it, and that the lower part of the "D" is lightly struck or polished off. That "D-minus" mark is found on Bren machine guns made at the Royal Small Arms Factory, Enfield. I suspect that mark was used on later revolvers in place of the more common script markings. The "T" is probably an "I" with the bottom lightly struck or polished off, and is the revolver Mark identifier, "I**".

Anyway, that's my story and I'm stickin' to it.

Buck