Here is a 66-1 that has a barrel measuring 6 1/8" rather than the standard 5 7/8". This change was made in 1979 prompted by pending changes in firearms legislation. This barrel change caused problems including the gun being disqualified from some competitions that required a 6" maximum barrel length.
Here is my Model 66, purchased in 1979 just after I was just hired as a Police Officer....
I traded with a pal for the stainless rear sight assembly, then added a white outline rear blade. I worked over a pair of Art Jewel rosewood stocks to a thinner, more rounded profile and to accomadate a speedloader. The S&W medallions were pried from a burned up pair of j frame stocks I found at a local shop. Turns out the medallions were off an old model 60 and were stainless too!