Helping a fellow at work investigate his family heirloom

we buy. I talked to an older gentleman a good while back as to which guns were worth any money or which ones could still be shot. He told me the short and sweet answer to that was "if the gun has a maker's name on the sidelocks or on the rear of the barrel, it would have some value, but only if it is in good working condition. Otherwise it is just an older gun that should be hung on a mantle". He mentioned that back in the early 1800s in just about every small town there were people that made those older guns pretty much from scratch and very seldom did they put their names or initials on the guns as gun collecting back then was non-existant. The people that made the guns were making then to be used and doing anything fancy was a waste of time. They were a needed industry back then as the guns served several purposes, including self defense and hunting for game to feed the family. As rumors of a British invasion got stronger the more guns these colonial gun makers cranked out and they served those purposes listed above.
In all the years we have been buying estates we have probably bought 25 to 30 of these old muzzle loaders and I only remember seeing a couple that had the maker's name on them and even then the names weren't a well known gun maker.
The older gentleman that is an expert on antique firearms told me to buy Flayderman's Guide to Antique American Firearms, that any question I might have will be answered in that book. And he was right. I have used it several times thru the years to help value an antique muzzle loader and in almost every instance the old muzzle loader was made by an unknown "colonial village gun maker".

That said, I had a Belgian without proof marks in .40 caliper at one time, so no guarantees. The lock and trigger look very similar.