A -2 & -3 for the mix. A factory 3" P&R'd,,, that would be pretty neat!.
Possible 3" P&R 66?? Model 66's started in 1970?. But went non-P&R in 1982 with model 66-2.
Model 19's also went non-P&R in 1982 (19-5). BUT,, some model 19's were made with 3" barrels as early as 1965 (19-2). So the tooling was there and the material was there,,,,,,???
As I will always admit,,, "I'm a student, teach me". One of my first lessons, " with S&W, anything is possible". Ten+ years of model 66 production before SOMEONE put together a 3"??
Photos of one would be great.
Just my rambling thoughts. Your mileage may vary,,,