This definitive non-denominated stamp from the Czech Republic features timber-frame houses. Z indicates the international rate. I have no idea why the letter Z was chosen. A is used for domestic mail, and E for European destinations. For more architecture on stamps, explore the links at Sunday Stamps.
Wonderful mail from Heleen that was a surprise arrival two days ago.
And inside one of her favorite postcards of her home country - stunning view.
I was very happy to see that both PostNL and USPS worked very efficiently for me to receive the letter on March 21st, with a postmark of March 16th, even in these tough times! Thanks, Heleen, it really lifted my spirits after what felt like one of the longest weeks of my life. (And I will answer your moon-related question in my next sending).