Richland was an importer, mostly of moderate quality muzzleloaders and I remember them from the 1970s though they may have been around longer than that. Given it's age and the fact it's brass condition would be the determining price factor. There should be a date code on the gun telling when it was made and it would be nice to know who made it. There's a good chance original replacement parts are unavailable but other manufacturer's parts can often be hand fitted. It's worth what you are willing to pay for it.