Very nice!!!!!  thats one I'd be proud to own.   

What is the cal.  With the rear barrel sight I'm wondering if it might be for one of the earlier larger bore BP target/hunting cartridges.  There were a gaggle of them in 9 and 10 MM variations,   they preceded the 8.15x cartridges much like our .38-55 did the .32-40

If the bore is good and the gun is shootable, and in a commonly available caliber (8.15x46r)  I'd guess 1500 would be a fair figure.  If it is in one of the older bigger -bore BP, cases and moulds can be a real negative issue for a shooter/customer, and a rifle like that just begs to be used in 200 yard offhand matches, not hung on a wall 

  FWIW steve Earle makes a nice clamp on base for target blocks that clamps to the barrel rib.  I have it one on several of mine.  no scratches no holes in an antique barrel