That is the way S&W used to make the things, you know, back when quality counted for something? "Pinned" refers to the pinned barrel. If you look at an old one you will see a small pin driven thru the side of the frame where the barrel screws in. It was supposed to keep the barrel from backing out. "Recessed" refers to the cut of the cylinders. They have a recess cut out so that the whole cartridge, rim and all, is inserted into the cylinder, instead of having the rim exposed as on the new models. Kind of hard to explain the recess. Basically, the back end of the cylinder holes have enough of a lip cut out so that the rim also fits into the cylinder. Makes the whole back of the cylinder flush or flat instead of having 6 buttons/rims sticking out.