Nice collection of 3" 66's. If your question is whether there were any other 3.25" 66's, I think there were some 3.25" with high - vis front sight 66-6's, which had the lock, IIRC. Regards 18DAI.

Edited to add: All the 66-5's I've come across had thicker, "heavier" barrels than those on my 66-3, and 66-4's. There were also true 3" 66-5's, but the front sight ramp did not go all the way to the frame, making them, IMO, not as nice looking as the 3" 66-2,-3 and -4. The last 3" 66's that had the front sight ramp go to the frame were the 66-4's for RSR.

Don't forget the Walther R99 La Chasse, which were simply 3" 66-5's with Walther markings, and the special run of 3" 66-5 Pintos.