Auction #93 Worldwide Air Post stamps and postal history, Zeppelin Flight items, philatelic rarities of the World

1928, Provisional Government paper money of 1,000rub (so-called Kerenski), in fact issued by RSFSR Bank, used as postcard-invitation to the Leningrad Oblast Philatelic and Paper Money Exhibition, franked by worker 10k brown, sent from Leningrad to Vladivostok, arrival ds is alongside, vertical fold, still VF and very interesting item, Est. $250-$300