Redonda

From Linn's "Stamp Issuing Entities Of The World" page.

Redonda (1979-91)

Stamp-issuing status: inactive; Population: 0. A steep, guano-covered rock one-half mile square in the eastern Caribbean between Montserrat and Nevis, owned by Antigua. Antiguan stamps overprinted "REDONDA" were introduced in 1979, with purpose-designed issues on a variety of popular topics following later that year. These were postally valid on Antigua, since Redonda has neither postal service nor inhabitants.