Look at some of the big auction houses like RIA and Morphy for the Model 1877 and you'll see where that one is an okay gun it's not considered a nice one comparably speaking.
I'm going to say from what I can see in that picture that gun might top out at $750 on its' best day and that is because of its' longer barrel than normal. $1500 is way out of the ball park and that blue book of gun values has cost many a new collector a bunch of money through the years. Look at directly comparable ones at what they actually sold for and that will keep you on safe ground. Also, there is a fair amount of difference between the value of one of these say made in 1877 or 1878 and one that is made in 1901. Antiques in condition for condition always bring a premium than those made after 1898.