I can't find much information about this flare gun beyond that it's of French manufacture and has a percussion cap ignition system, thus dating it to probably the Nineteenth Century. The cup at the end, I gather, is used for the flaring material. But I'm at a loss to figure out how the flare would be propelled.
How do you think this flare gun works?
Link | Photo: Charles Miller Ltd.
There are a few Civil War examples here: http://armscollectors.com/mgs/flare_pistols.htm