The NRA is able to tell you most everything you want to know about most any gun. They've been in the mix since 1871; if they don't know it, it's probably not worth knowing. This is a member service they provide. You need to send them markings off of the gun (a description of what markings, stampings, etc. are on the steel and stock). Photos are, of course, helpful as well.

If you're not in the NRA you sure should be, for many, many reasons besides this.