My bet is a 2" converted, Ive done several like that and changed several back to 4" guns for officers. The 2" frames topstrap is even thicker than a model 14, so it leaves a little step down to the barrel. That and the sight are the giveaways. Factory may have done it but they started with a frame from a 2" model. They all shot great and the longer barrels look nice on the gun.