I am NOT an expert on the Colt Dragoon. I've never even owned one!
But I did once own a real and untouched Dragoon stock, authenticated as to all aspects. These photos are old and don't show all the details you would want to see (such as the knurling on the thumb nut which is not visible) but you can see this is an untouched stock with some original blue still on it. See how he wood to metal fit looks better than on the photos of the one under discussion.
These stocks were ordinarily supplied one stock to every two revolvers, and so the stocks do have two serials on them, the serials of the two revolvers.
Charles Pate has studied Colt percussion revolvers for decades. He wrote the book on the model 1860 (and this includes his study of the shoulder stocks for the 1860), and is now writing the book on the Dragoon Model.
He and I have traded thoughts for many years on various 1860s we may have seen only in photos - he knows what he is talking about.
Because the shoulder stocks are so rare, he has typically looked very carefully at listings offering them.
I would say that if Mr. Pate saw some parts of the stock were not Colt parts, the serials looked restamped, and the gun with it had "several problems" I would not consider buying this.