Martini Henry Mk IV Pattern B(?) Markings

I recently picked this up. The only information I have on it is that it came to Canada from somewhere in Africa back in the 1970s.

It's the additional stampings I am curious about.
1. Numeral "37" with stroke through it
2. "RAM 850"

Anyone familiar with African colonial markings can help explain these markings? Attachment 105268
Thanks

The pic looks like AMR 850!

Most MkIV Martinis I've seen have been from the Nepal cache and have British and Indian arsenal roundels/markings and such on the butt-stock plus clear Nepal markings on stock and metal.

Sorry, you are correct. It is actually "AMB." Must have been tired. Will correct above.