Nice looking rifle.

I notice that the recv'r ring pic of the 1900 in kuduae's post has the same repair in it that the OP's has. An old scope base dovetail fitted with a blank, shaped and matted to hide it.

Doesn't really mean anything, just an observation.

Didn't know that about the firing pin retaining nut spring on the 1900 nor the early style cartridge release tab placement.

Thanks for all the postings..great pics.