Aging a Reproduction Civil War Canteen

I have a nephew that is an avid Civil War re-enactor. He's recently purchased a couple of items (a canteen and a handled mug) that have a very bright finish. (nickel plate?) He wants to make them look old, naturally. How can it be done? How can I determine exactly what the metal or plating is?

I would recommend a paint made by Krylon called a hammered finish. It comes in a spray can, and the paint dimples when it gets thick enough (several passes of the spray). It gets bumpy, and looks kind of old.

I would not recommend aging chemicals for a canteen or drinking cup since, of course, we worry about drinking from them. Also, we don't know the metal, which makes it hard to recommend an aging solution, since each metal reacts to different solutions. For instance, silver turns black with sulfides.