20 pfennigs medium violet ultramarine, with on envelope very rare plate flaw IV: "wide notch right besides of the lower central tip", on forerunner letter to Niederuzwil to Switzerland, cancelled by single circle postmark "KAIS. German. P. A. CONSTANTINOPEL * 5 / 7 / 81 2-3 N. ", perfectly preserved folded letter cover with arrival postmark from NIEDERUZWIL 10. VII. 81, route was over Parma, unsigned, photo expertize Ronald F. Steuer BPP (2022) "all postmarks genuine and date-appropriate", Michel no valuation