373rd Auction
23-27 June 2020 in Wiesbaden
1906, essay for reply envelope with window for the value impression of the response envelope, to that the reply envelope with two different impression “Timbre imprimé sur l’enveloppe” and “Timbre d’affran-chissement”, window envelope with tears at top, otherwise fine, sample presented on the UPU Conference in Rome, very rare “pair”