I'm a relative newbie to the world of S&W revolvers, (my collection currently includes a 442 and a .38 special 640,) and I was just wondering:

Which models of S&W revolvers were only manufactured with the internal lock system? Similarly, which models are "hard to find" without the lock?

I ask this question because I am on the lookout for a 640 or 649 in .357, and I keep hearing that these models are hard to find without the internal lock. Are there any others that were mainly built in the ILS era?

(To keep it simple, why don't we focus mainly on the .38 /.357 models.)

TMann