Cover of registered letter sent from Moscow to Vienna (Austria) on November 2, 1926. Letter passed foreign exchange control, tax paid by stamp РЕ 12, perforation 11 1/2 (for attachments with value up to 1000 francs). Pair of air mail stamps (with "10 k. gold/10 коп. зол." surcharge) on the front side of the cover. Left stamp has variety - "narrow zero".