Usually, an unsigned contemporary muzzleloader is one built by a black powder hobby enthusiast for himself. Contemporary gunmakers in the business will either engrave or stamp their name or initials on the barrel's top flat between the breech and the rear sight. Occasionally, it will appear on the next flat left of the top flat on a right-hand gun.
A gunmaker's rifle or fowler is his "business card". A signed gun will be one either made for a customer or one that the gunmaker made to sell to the visible public at a shooting match, for example.
There is one other reason for an unsigned firearm and that is a case where the customer prefers to supply the parts, and hires the maker to build it for the customer. The maker will either leave it unsigned or he will stamp/engrave his name on the bottom flat hidden by the forearm. In some maker's eyes, having the parts provided for him, "robs" him of the profit he would have made had he supplied the parts since he usually buys in quantities, i.e. six barrels, six locks, etc.
The gunmaker may find himself needing the money and he doesn't really like the parts chosen for him, but he could use the cash to assemble the firearm. So, the two agree to an unsigned gun. Here is an example of an unsigned flint double that I bought at the NMLRA Southeastern Rendezvous in 2013. Beautiful execution withe Ed Rayl barrels, L & R locks and gorgeous walnut, professionally finished, but unsigned. It was a mystery that was never solved.
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