[Jim]

Most authentic and documented WW I material is quite rare and very pricey. You can find a few books that were printed in very large numbers for modest amounts($20 to $50 range) or postcards or widely produced photos from the era in the $10 to $50 range, or a picture frame made from a chunk of a propeller, or such, but something like an aircraft serial number or other desireable object will typically sell for thousands to tens of thousands.

Undocumented objects are easy to come by but you should expect that 99.9% of these are either fakes or later items from the 1920s or 1930s. Great war aviation souvenirs were avidly collected during the war and have been ever since. The supply is far smaller than the demand so fakes have been made since the start to meet the collector demand. Many of the old fakes have some real age to them so they are harder to sift out. Most of the dealers in old militaria can not tell what is real and what is not, though they would strongly disagree with my statement. That is what I have personally found though. If you buy from such a person, or if you buy at an auction you need to keep one demand non-negotiable - you need to insist on some rock hard provenance. And a statement from a collector that it came from their personal collection or a statement from a dealer that they guarantee authenticity is not very substantial provenance. You need something like a photo of that actual object from during the war, or you need to buy it directly from the relatives of the old pilot or such (though even that can be a bit dicey since family stories always grow with each telling). You also need to educate yourself by spending time in museums really studying the kinds of things you are interested in collecting so you will be able to judge intelligently whether to believe the story that comes with an object.