I'm usually pretty good with deciphering military marks on weapons and gear, I have books, hand compiled lists going back to when my grandfather dealt with them, and tons of right clicked PDF spreadsheets

That said, I currently have an enfield (no5mk1) that has a numbered broad arrow, specifically 13/|\, and I can't find anything in the stuff I have (there's a good possibility I have it but just can't find the right list) about it.

What I do know is that it was field refurbed/repaired at unit level, eventually sos'd, and imported pre 68. But the 13/|\, which is on the rear of the left receiver wall is vexing me. I don't need to know, but I would like to.

Anyone have a good source for numbered b/a stamps on small arms?

Yes, the best work I have seen is "The Broad Arrow" by Ian Skennerton...

Covers pretty much all British markings...excellent book...