The photos are a bit hard to interpret. Overall shots of the entire piece of each one would help.
From what I can see, the 2nd looks like it might be a conglomeration of parts from various French or US flintlock muskets slapped together to make a wall hanger. The barrel is a forced match to the lock and the stock. It appears to have had a lot of welding done in the breech area to build up the breech diameter to get it to be close to the width of the stock, the barrel does not fit the stock inleting, and the shape of the breech indicates it is probably from a percussion or even later era gun. If the picture of your hand holding what looks like a pipe, is the muzzle of the same gun, then the barrel is way to thick walled to have ever been a flint lock barrel. My guess is this is a recent, i.e. last 40 to 50 years, parts bash from random, reproduction or possibly old parts, to make a wall hanger.
The posted photos of the third gun looks like a very recently mass produced and inexpensive American / Pennsylvania styled reproduction flintlock of indifferent quality. The photo of the Miroku logo and serial number don't seem to fit in with the rest.
If these are representative of what your friend has, it seems that they have obtained a cache of recently made reproduction guns. So far the Miroku Brown Bess is the only one that would be worth trying to sell, if that's what they want to do.
Mike