Me personally, I'd stick with forms of gold that Americans would easily recognize for the very reason you just mentioned about reselling. That's one reason why I sold all of my foreign silver coins, because I don't know much about foreign coins anyway and figured the average American would probably know about as much as I don't as well.
gold is gold, and those French 20 francs are collectable too, great deal I have some and there's a big Market in Europe. If you don't think there's a Market in re USA list it to ship to Europe on eBay, and you'll get plenty of buyers