How many S&W products made during the time you mention do you own? I have eight revolvers from that era, they are flawless. All of them are stainless and all had heavy DA triggers, but the SA trigger pull was superb right out of the box and the DA pull was fixed with an after market main spring/trigger return spring set that cost $14. Model 629 revolvers will digest heavy loads better than anything made before, especially the ones made in the 50's and 60's. The 625's rule IPSC and IDPA revolver classes.
I took a look at a factory new Mountain Gun during those couple years and didn't buy it because it didn't look "right". Bought a used Mod 29 instead.
Hey, maybe it was an abberation.