A copy of the Winchester work order from Cody will be the definitive document. If I read between the lines of your Post correctly, Cody only told you the Model # verbally and not specify whether the gun was straight or pistol grip.
In response to whether or not someone will turn down the gun, if a collector and someone has changed the grip, certainly, if a shooter and the work/wood is substandard, most likely. You need to obtain a copy of the work sheet and if the descrepancy still exists, you would need someone familiar with Win 21 to give you an opinion if original or not. These old Winchesters have been around a long time and if actually used as a Skeet gun, most likely was refinished at some time. Only an experienced collector can give you an opinion if refinished as one of the virtues of the Model 21 is that they are easier to refinish and refinish well.
BTW, I once owned a 1939 16 gauge Skeet with pistol grip that had been totally refinished. It was very nice. You might also check my WebSite for additional help.-Dick
