In 1875, the colony of British Guiana in South America used its own postage stamps with an overprint reading ‘OFFICIAL’. There were 5 different stamps like this in 1875 — 1 cent, 2c, 4c, 8c, 12c, and 24c; a 48c version is thought to have been used only later, as a surcharge in 1881.
British Guiana again used ‘OFFICIAL’ overprints on stamps in 1877, this time in values of 1c, 2c, 4c, 6c, and 8c. The 6c is particularly rare from this set.
In 1881, stamps were overprinted for official use a third time in British Guiana, but these were surcharged — a large numeral gave the new value (in cents). These surcharged ‘OFFICIAL’ stamps are considered separately from the 1875 and 1877 issues by many collectors.