jsconnnor1:
Value varies greatly on condition. In 2006 in very good condition the Standard Catalog of S&W gave a value of $265, plus 25% for the S prefix, plus 25% for the 2 inch barrel. Photos will help value it, Oro, Old Fuff or Saxon Pig will probably have a better idea on current values - I am in Australia and can only go by the book.
Tex62:
Between January 1983 (ABLxxxx) & October 1982 (ADExxxx). The Model 64-3 .38 Military & Police Stainless was produced from 1977 to 1988. The pinned barrel was deleted in 1982, so yours will be a crush fit barrel.
Flamingtaco:
mnrivarat was correct, one of the serial number ranges for 1972 was 3K31280 to 5K6616. The 15-3 K38 Combat Masterpiece was produced from 1967 to 1977.
It isn't unusual for old guns to be well looked after, back in the 60s and 70s they took a lot more of the average man's disposable income to purchase and tended to be cared for as a result.
Also a lot of carry guns are carried but rarely fired. I have a 1971 Model 66. I'm confident that I've put more rounds through it in the last five years than the security company that had it for the previous 30 or so.