Good looking gun. I worked for Robert Watts for a while. He used the small ,large Siler locks,on his southern guns, Bob full well knew that an english lock would be the most correct. His iron mounted guns are beautiful. Bob would sometimes English them up. Bob was most interested in how they shot, won matches. Putting a much more costly lock, that he would have to completely rebuild, was not in Bobs logic. So unless you are making a bench copy, use the the Siler file the pan, do some english looking stuff. Be happy . 2 lock bolts on a late flint? It could be either way. If you dont know who Robert Watts is, Ask some of the older shooters, Like I said your gun looks good.
Ron Brimer