CX1AK 1957 Uruguay

Uruguay is divided into nineteen departments, including the capital. On the back of the card is a map of them. The same map, with a list, is on Wikipedia. But this one shows the prefix allocations.

The calls are identified by the first two letters of the suffix, not by one-two-three-four, etc.

Montevideo, the capital is ( number irrelevant ) AA to CZ
Artigas is KA to KZ. Rivera is PA to|PZ. Colonia is FA to FZ. Etc.
If you look at the map there is a pattern ( although not entirely consistent ) going upwards, from Montevideo at the bottom.

There seems to have been an award for working them all at some time; the C-19-D (Confirmed 19 Districts?) at top right on the front of the card.

QSL & Info G4UZN Collection