The 4" is a -4. I bought it brand new in 1978...still have the box and invoice. The 2.5" is a -6 (1982). I bought it at a gun show in 2007. Both are great shooters and they' re my favorite guns.
I have a Model 15-2 K695XXX. It has a target hammer and target trigger. It's in good shape and shoots fine. Is there a way to find the appox. age and value of this gun?