I just received this postcard from the 22nd World Esperanto
Congress, Oxford, England, 2–9 August 1930, which I bought on eBay
The card features a photo of New College, Oxford, with an English caption on the picture side and an Esperanto caption on the message/address side. The stamp, Scott #189, was cancelled with the congress postmark, unfortunately not positioned fully on the card.
The card was written by a Czech Esperantist, whose signature is illegible, and mailed to his Esperanto club back home in Prague. The pencil scrawl on both sides of the card is difficult to decipher, but the beginning of the message is significant: "Aldonante la subskribojn de la filino kaj frato de Dr Zamenhof…" ("Attaching the signatures of the daughter and brother of Dr Zamenhof..."). And there they are, above the salutation on the left side, the autographs of Felikso (Felix) Zamenhof and Lidja (Lidia) Zamenhof, the brother and daughter of L.L. Zamenhof, the inventor of Esperanto, both of whom were active Esperantists themselves. They're the two people on the left in the photo below, which was taken at this particular congress.https://eo.wikipedia.org/wiki/Felikso_Zamenhofhttps://eo.wikipedia.org/wiki/Lidja_Zamenhof