A triptych is a philatelic

Philately

Philately is the study of stamps and postal history and other related items. Philately involves more than just stamp collecting, which does not necessarily involve the study of stamps. It is possible to be a philatelist without owning any stamps...

 term (from the Greek: "three" + "fold") which was borrowed from the art world and having the same meaning: a set of three panels hinged together. It is used to describe three se-tenant

Se-tenant (philately)

Se-tenant stamps or labels are printed from the same plate and sheet and adjoin one another, unsevered in a strip or block. They differ from each other by design, color, denomination or overprint. They may have a continuous design. The word "se-tenant" translates from French as meaning "joined...

 postage stamp

Postage stamp

A postage stamp is a small piece of paper that is purchased and displayed on an item of mail as evidence of payment of postage. Typically, stamps are made from special paper, with a national designation and denomination on the face, and a gum adhesive on the reverse side...

s of related design that make up a complete single design.

In the US, the form is rarely used, perhaps because it does not lend itself to the popular plate block of four format for collecting. Instead, one frequently sees blocks of two or four or other even number of se-tenant stamps. In 1976, the US produced the "Spirit of '76" issue. In 1992 for the 500th anniversary of the discovery of America by Columbus

Christopher Columbus

Christopher Columbus was an explorer, colonizer, and navigator, born in the Republic of Genoa, in northwestern Italy. Under the auspices of the Catholic Monarchs of Spain, he completed four voyages across the Atlantic Ocean that led to general European awareness of the American continents in the...

, the US issued a series of five triptychs in vertical format based on the famous 1892 series of commemorative stamps. This was a triptych only in the sense that they were thematically related to each other, but they were distinctively three designs rather than like the continuous design of the Spirit of '76.