Yes, it is pinned through the side. Sometimes if you puff warm breath on the area, the pin is more evident. If you find one of these knives stamped Buck only, and you cannot see the pin, it may be one of the early production "barrel-nut" models which Vern Taylor alluded to. These usually have a plug circle visible in the butt end of the pommel although I have one or two which did not need the plug. The lack of a pin through the side of the pommel is the most reliable method of observation to differentiate between the two production types. Any of these models with a two line stamp, three line stamp or year symbol are flat-tang construction and will not have the barrel-nut.
BUCK / U.S.A. = TWO LINE
BUCK / MODEL # / U.S.A. = THREE LINE