(If you'd like to learn a bit more about the Ceremony of Carols, my choir director wrote an good article about it for the church newsletter that you may want to read. And if you want to know a lot more, these program notes by another Presbyterian church choir director are worth reading.)
I chose today's card with A Ceremony of Carols in mind. It's more a Renaissance style than a medieval one, but close enough. In any event, the card is almost exactly as authentically medieval as the Ceremony itself, in that it was made in the first half of the 20th Century by Buffalo woodcut artist J. J. Lankes. I don't knew precisely when this card was designed, only that it was "made between the 1920s and 1940s." So ... the 30s? I doubt that's what they meant, though.
Grosvenor Rare Book Room, Buffalo & Erie County Public Library, Buffalo, N.Y.