I think this subject could be a major article and when I get a week with nothing else to do I may write it!
Meanwhile here is a list of some things to look for:
Double pin holes where guard and ramrod pipes were redrilled on new stock. (The absence of double holes does not prove the rifle is not a restock because some times they hit the old hole perfectly.)
Lower butt moulding filed through the butt piece but no corresponding moulding on the stock. Both Kindig and Shumway tended to ignore this obvious clue -- perhaps, in George's case, to avoid conflict with the owner.
Interupted engraving along the butt piece edge of the patchbox. Often a restocking involved bending the butt piece to a greater curve to be more "up-to-date" but even if it wasn't bent getting the already engraved box to match up perfectly was not easy. They often just let it hang over a bit and trimmed it off.
Also on the butt piece--to make the rifle more up-to-date the butt pieces were sometimes made narrower. This often results in a buttpiece that is thicker than normal along the finished edge. (You need to develop you eye for spotting this because many re-pros are too thick as well and you may not have noticed.)
Stock design that doesn't fit the regional style or period of the mounts, barrel, & lock.
Single screw lock with a two screw side plate or vice-versa.
Barrel set back (shortened) at the breech but there is no evidence in the stock of earlier loop or pin placement. Like wise a barrel slashed for a front lock bolt with no corresponding evidence in the wood.
Like I said this could be a long article or a long seminar!
Gary