Welcome aboard from ol' Wyo, Elisa.
According to lore a Lady named Flora Mason Van Orden, co-owner of Evaluators Limited Gun Shop in Quantico/Triangle, Virginia, "designed" the S&W Combat Masterpiece after WW II.
Flora and her husband George owned the shop, and she was a good friend of S&W president Carl Hellstrom.
When S&W assigned model numbers in 1957 the Combat Masterpiece took on the added identifier of Model 15. Yours went through three engineering changes. The Model 15-3 was built from 1967 through 1977, and S&W likely shipped yours in 1975.
Does yours have a 4" or a 2" barrel? Is it blue or nickel?
Value is dependent upon condition. Very nice ones are running more than $700 +/-.
Hope this helps.