Caspian made all of the slides and frames for them original GSR models. They were plauged with lots of reported issues, both cosmetic and functional. Sig blamed Caspian for out of spec frame and Caspian said Sig was at fault. Sig then moved slide and frame production in house, and released the GSR Revolution series. Caspian was, i don't know if they still are, selling off remaining frames and slides that were not talken by Sig.
BTW, I own a railed Revolution and feel it is the best 1911 in it's price class, and one of the nicest 1911s I've ever owned, period. TRhere are still a few complaints of problems (but who hasn't read complaints of Kimber, or Smith, or Springer 1911s for that matter.) But when you read some people posts of GSR issues, it's not always obvious if they are referring to the "first series" GSR or the newer Revolutions. As for me, I have absolutely no problem reccomending a Revolution to anyone. Check one out in person when you get a chance.