Well, since this thread has expanded to include all Model 66s, I might as well throw my three into the mix. I'm not as skilled with a camera as some of you, however.
From top to bottom, they are a 6" 66-2 with Ahrends Retro Target stocks, a 4" 66-2 with Ahrends Retro Combat stocks and a 2-1/2" 66-4 with Ahrends Retro Combat stocks. All three have the red ramp/white outline sight package and the 6" and 4" have target hammers and triggers.
When I posted a photo of the 4" gun before, some one contacted me for the serial number. It seems it is somewhat of an oddity in that it has a trigger stop.
Ed