I really hope someone on here can help me out.

I recently picked up a 1936-vintage A1-grade B25 with a few non-standard (at least non-catalogue) features that I would like to research a bit more closely if possible. I know it was originally ordered by someone in the US so I'm hoping there's someone in the US with some form of records of special-order B25's that would be able to help me out or steer me in the right direction.

Much obliged.

Long shot, but might give Midwest Gun Works a call and see if they could help or perhaps point you in the right direction. They are an authorized repair center for Browning and friend of mine just had them do some work on his B25. Just a suggestion.

Browning Historian Glen Jensen will tell you what you have and where it came from

Glen has retired a year or so ago.
Your best bet is Shotgunworld.com.
Go to the I love my browning forum.