I'm not an expert by any means on antique rifles, but I have two Winchester rifles that have been in my family for many years. One is a Model 1873, 44 cal carbine and the other is model 1876 45-60 with a 30 inch barrel. I noticed in an ad about an auction (Rock Island Auction Co.) that the estimated auction prices ranged from tens of thousands to $275,000. What/how are these values figured? This seems like such a wide range of values but there's no indication of just what features, conditions etc actually allow one to figure value.