Bidspirit auction | Worldwide Air Post Stamps and

Worldwide Air Post Stamps and Postal History - Soviet Union - 1933, ''Stratostat USSR 1'', 5k, 10k and 20k, three covers franked by these stamps, the first one sent from Moscow to Stalingrad, second one - locally sent in Moscow, the last one - from Baku to Kashira (Moscow Obl.), mainly VF, Est. $300-$400 , Sc. #C37-39