Major engineering changes were afoot.

Regarding the pinned barrelsand recessed Cylinder being discontinued you will get a few different years. I have heard 1881, 1982 and even 1983.

I think the reason is because some guns took longer to make the change than others.

The 629 was pinned and recessed until 1983, the model 29 stopped being pinned and recessed earlier than that.

In 1980, you als had some new generation Revolvers like the L Frame coming over the horizon.

Plus 1980 was the year that Disco officially died.