I am doing research for a new book on postage currency, which I definite as either:
-Stamps that circulated as money as-is (Serbia 1915 issue for example) -Currency based on postally used stamps with differences (Russia/Ukraine with inscription on back, Greece 10 Lepta 1922 etc etc) -"Banknotes" with stamps affixed for verification (Marshall Hole issues from the Boer War)
I am looking for anything that would fall in these three categories, including oddities, errors, imperforates, specimens etc etc. My research does not include banknotes printed in the shape/form of stamps but had otherwise no postal relation, nor do I include encased postage as that would be enough for a book on its own. I have a fairly good idea of what exists but there might be local issues I am missing. If you have anything that you think would fall in this category, I would appreciate a picture (credit given, of course).
Also if anyone has any newspaper articles and other sources showing how these were used that would be fantastic. Because a lot of these circulated in countries whose language I don't speak, I have found very few contemporary sources.
The research does not include fractional currency, as these were never used postally even though the basic designs might have been similar. Encased postage is also not included, as I consider those more related to coins and there is a plethora of reference works out there already.