I have a couple of '49s and they are the round butt design but I'm not sure when Colt switched to that. The one at the pawnshop is probably an early model, which would be pretty cool. I think the first official year of the DS was '27.
That sounds like a good price if it's in good shape and unmolested. Especially for an early one. I have one, but it's the later model with the shrouded ejector rod. Check the action out good. It's getting hard to find a 'smith these days that know Colt internals, so you could get upside down real quick if it has to have work.
Its a transitional 2nd Gen. Still having the full grip frame, but showing the 1/4 moon front sight. Your only option for grip ajustment is one off custom or using a Tyler T-grip. The full 2nd Gen has the shorter grip frame allowing for all the modern grips out there now.