The 15-2 was introduced in 1961 and was produced until 1967 when the -3 came out. Is that serial number preceded by a "K"? (The "K" is actually, and legally, part of the serial number.) If so, the gun was shipped in 1967, so was late in the production run for the -2.
ETA: I see Targets Guy beat me to it. Gotta learn to type faster.