17th 18th century buffet.

I got this piece 13 years ago from a millionaire that i was moving. He told me that he had paid 2500.00 for the piece 25 years ago. He didn't really know anything about the piece. This piece is 7'long, 3' tall and 2' deep. I believe it is made of walnut. All the hardware is made of iron and its fastened together with iron spikes. Two of the front doors have sheild crests on them and there is a roman numeral number 8 carved in the back of the piece. I am interested in selling it but don't know what it may be worth. Any information would be very helpful. Thank you very much in advance and God bless you!