Peeve88: Your gun was made in 1978-79 in the serial number range 25k0001 to 56k9999. It is built on the K frame, S&Ws medium frame that has remained in production since 1899 in a variety of models and calibers. The majority of police and service revolvers from the last century were built on the K frame. What you have was designed as a target or training gun.
If it has a four inch barrel with a ramped front sight, then it is a Model 18 K22 Combat Masterpiece. This was basically a .22lr version of the very popular model 15 service revolver in .38 special. Think cheap practice and a great holster gun for walking around on a farm or in the woods.
If it has a 6 inch or 8 &3/8 inch barrel with a square cut Partridge sight then it is a Model 17 K22 Masterpiece. This is the .22 target version of the K38 Target Masterpiece revolver popular at the time for centerfire bullseye competition, The K22 & K38 .were designed to have the same weight and balance for ease of cross training.
The K22 has been in production in various forms since 1931, when it was introduced as the K32 Outdoorsman, it continues today in a much modified form as the 617 in stainless steel with a full length barrel under-lug and the option of a ten round cylinder.
The model 18 was produced from 1949 to 1985, when the four inch Model 17 was introduced. A four inch stainless steel model 617 is still available and S&W are offering the reintroduced model 18 Classic this year - if you have a thousand dollars to spend. :P