1935, 10 C. Airmail, overprint dull, block of four in mixed franking with 20 C. Airmail green on properly franked home letter to the 1. Winter airmail in the Bündner alps, flown Zurich - St. Maurice - Zurich, faultless preservation. (Zumstein No. F19 b, F4.1.09 s Fr. For lots already 480.-)