Dave,
No one can comment on the pistols until you post some photos. As far as the case goes, GOOGLE "dueling pistols" on the internet and a number of sites will come up showing antique pistols. Most of them have French and Belgian pistols in their collections or for sale. Often they have good photos of the cases. French and Belgian cases were usually different than English ones. The pistols and accessories (powder flask, loading rod, oil bottle, flint whisk, bullet mold, screw driver) had individual cut outs that precisely fit the shape of the item. The cases were often lined with velvet. English cases had wooden partitions that roughly outlined the items and were lined with wool baize.
dave