Colt 1851 , 12XX SN Go to guy for sale

A friend has an 1851 Navy. Ok shape for its age, I have a hard time putting percentages on old guns. Low 4 dig SN, Square back triggerguard. He wants to sell it and thinks the local dealers are trying to take advantage of him has been offered $1000-1200. Is there anyone you would reccomend for an appraisal, or a collector of Old colts such as this?

My border collie is smarter than your honor student.