Here is an extremely rare card from the Spanish Civil War in 1937. Inside it reads:
With the Season’s Greetings
Christmas… 1937
New Year… 1938
From the Volunteers of the 15th International Brigade and Their Brothers in the Spanish Republican Army
British Battalion • Lincoln-Washington Battalion • Mackenzie-Papineau Battalion • And Spanish Volunteers.
The Mackenzie-Papineau Battalion (the “Mac-Paps”) were the Canadian volunteers who fought against Franco’s forces on behalf of the Spanish Republic.