1936, 40 C on 90 C. airmail, overprint orange red in mixed franking with 30 C. on 90 C. on registered airmail cover from "Zurich airfield 23. VIII. 37" to Bern, reverse arrival postmark from Sequence day, rare, certificate Liniger, (Zumstein No. F23, F24 a s Fr. 1.200.-)