If you really want to know about Remington SxS, the guy to get in touch with is Terry Deem. I don't have his contact info but I think he is somewhat active of the Remington Society forums. He was a friend of Mr Semmer and has effectively continued Semmer's accumulation of the knowledge available on Remington.

I have Semmer's book and it's a great reference but it's now around 20 years old and could really stand to be updated. Lots of new information has come to light in the last 20 years

The world cries out for such: he is needed & needed badly- the man who can carry a message to Garcia