MAC is pretty much bottom of the barrel where French guns are concerned. If "excellent condition" means it's tight (no wobble in the barrels with the forend off) and no pits in the bores, it should be worth $300.
One other issue would be chamber length. If the chambers are 2 1/2" (good chance on a French 16), you've got an ammunition problem. It will probably handle 2 3/4" 1 oz loads from Win/Rem/Fed, but you probably won't like the recoil. If you don't plan to shoot it much, order a flat of 2 1/2" shells from RST. They sell both 7/8 and 3/4 oz loads as well as 1 oz. Not much more expensive than buying the cheapest 16's you can find at your neighborhood big box or sporting goods store.
