1873 Whitmore Hammer Lifter

[RCrocker]

My great grandfather owned a grocery store in Madison, WI and hunted ducks on Lake Menodota before the turn of the last century. He sold the ducks in the grocery store. I recently acquired his gun. It is a 1873 Whitmore Hammer Lifter with Carbonized steel barrels. I think it is a Grade 1. The serial number is 2756. While I am not interesting is selling it, I am curious as the ball park value to a collector. Any information would be greatly appreciated. Thanks

[DavidFagan]

Condition - This is needed for someone to help.
It's decarbonized, there is a good article on http://www.remington.com by Charles Semmer.