Costa Rica 1883 Coat of Arms "MUESTRA" Overprint Set

Costa Rica · 1883 · 1c, 2c, 5c, 10c

This set features four definitive stamps from Costa Rica's 1883 issue, each depicting the national Coat of Arms. The stamps are overprinted with the word "MUESTRA" (Spanish for "Sample" or "Specimen"). These were not valid for postage but were distributed to other postal administrations through the Universal Postal Union (UPU) to identify valid stamp designs.

Specimen stamps were a key part of the Universal Postal Union's system in the late 19th century, ensuring member nations could recognize legitimate international postage and prevent fraud.