I found a razor on Ebay that was in fact a civil war era razor. The manufacturer existed only from 1860 until 1875. That didn't mean that the razor had anything to do with the war, and, because of the manufacturing dates, could have been produced after the war itself. Still, the information I had was enough for me. In your case, you have only the opinion of the person who is trying to sell it to you. While the seller might be correct, there is no documentation or evidence for his claim. I'd pass without better evidence.