ST or TS means Target Stocks
In 1980 the Target Stocks would have had the football cutout for speed loaders and black washers.
EDIT:Only an S denotes service type magna style stocks
That would be silver washers past 1972
I use to believe that time frame you mentioned,since I have a set of black washers that are original to a 1980 gun.I have since learned here of a different time frame of black washers used up and disappearing around 1972.I would prefer your time frame since I cannot figure out how an 8 year old factory set of stocks made it onto a 1980 vintage gun.And I did know the gun and original owner ,and it did ship with those black washers.Thanks for the feedback on the time frame.Once stainless revolvers were being sold silver washers were made for them.
The earliest silver washer stocks were made for the stainless revolvers but blued guns continued to use the black washer till stocks were used up around 1979-80 +/-
Target Stocks lost the washers in late 1985 and at about the same time bar codes began to appear on end labels.
Only original gun owners can say for sure which stocks were shipped on their guns from the factory in transition periods that often lasted a few years.