What do you make of this M1903MkI USMC rebuild?

[ssgross]

What is SRS?

Rifle is in Canada, if not obvious. There is no cache here for usmc springfields vs any other 1903, I think it’s unlikely anyone up here would bother to fake such a thing.

Apologies - I thought with the frequency of requests from folks asking to look up their serial number the SRS books were common knowledge. There are 4 volumes. Here is a very good description of what they are, where they came from, etc.
https://www.gunboards.com/threads/sp...-they.1192966/

In a sentence or two, some people (see the link above for who) spent years combing through national archives and/or other document sources, and whenever they saw a serial number they made note and summarized its source in tables. The 4 volumes, long out of print, fetch very hefty prices on fleabay. I just happened to finally acquire all 4 volumes this year this a very nice guy at an even nicer price.