I currently own two Smith's. First one is a model 19 2 1/2" barrel (mid 80's vintage) with no lock and the other is a model 586 4" with lock. The 586 is a joy to shoot and almost exclusively gets fired double action. I did a little smoothing and polishing of the rebound block (also replaced the rebound spring) and that makes a world of difference in double action trigger pull. Backing off the strain screw on the main/hammer spring helps. Just got to be careful with the hammer spring, that too light and you will get misfires. As far as I can tell the lock mechanism is just a cosmetic difference and it doesn't bother me.
Paul
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