I need help with a Smith and Wesson 15-3?
The -3 version of the .38 Special Model 15 was made from 1967 to 1977. It's essentially a "carry" version of the Model 14, which was originally - prior to model numbering - the K-38 Masterpiece target revolver. The Model 15 was originally known as the K-38 Combat Masterpiece. Because it was intended for defense rather than target work, it originally had a shorter 4" barrel (and later came both longer and shorter barrel lengths) and a ramped front sight, rather than the squared-off Patridge style target sight.
They are very fine guns. I have one from 1970 and it's on my list of "guns that I will never part with." If you post the serial number, x'ing out the last couple digits if you like, I or someone else with the book will be able to look up a year of production for you; and if provide details on barrel length and condition (or better yet post photo or two) we can give you an approximate value.