Three Zeppelin Balloon covers were just obtained. They cover the history of the Hindenburg balloon, including the disaster in May 1937 (50 years anniversary).  Rare cachets, not seen before, must be scarce. These are Aerogramm covers with prestamped 65c + Automat stamp + the Stanley Gibbons 1109 with the Salvation Army “Helping Hand overprint (SG 1138).