Glock21SF: Your 10-5 dates to 1969-1970. Your 65-5 dates to between August 1996 & August 1997.
In 2006 the Standard Catalog of S&W gave a value of $400 for as new in the box, $300 for excellent condition. It gives no variation for a three inch barrel.
Personally I think you did well. They aren't made anymore, so a like new condition second hand one is a good find.