That is a 66-5 RSR Stocking Dealers Special. Its actually a 3.2 inch barrel revolver.
S&W also made a true three inch barreled gun for Lew Horton, but in a very limited number. Don't know the value of the RSR, but the Lew Horton guns are sought after collectibles.
I believe S&W made the three inch Model 66's in the dash 2, 3, and 5 variants. They made a very limited run of 66-4 guns for Lew Horton called the "Super K." It was a performance center gun, with a contoured, slab side, barrel and magna ported. They came with the round butt faux ivory grips from the factory. I've only seen one and I foolishly let it get away. They made 167 and they sell for insane money today.
The most prolific of them is the 66-2 guns made for Ashland Distributors and even though more were made, they are sought after and hold their value quite well. As the dash 2 guns were the first three inch guns, I don't believe any were ever pinned and recessed as the no dash and dash 1's were the only pinned and recessed Model 66's.
This is the Model 66-2 Ashland, three inch. It came with magna grips. The grips on this one are actually what shipped on the 66-4 Super K and the 66-5 Lew Horton guns.
This is the Model 66-5 Lew Horton, three inch, wearing the wrong grips. One of about 293.
