Men’s Heraldic Surcoats
Osprey Men-At-Arms: Medieval Heraldry

Tournaments: Jousts, Chivalry and Pageants in the Middle Ages

Osprey Elite: Knights at Tournament

Reconstructing History: 14th Century Jupon of the Black Prince Pattern

Some of the variety of styles of heraldic surcoats, tabards, jupons, and cote-armors worn by men in the Middle Ages. These are worn over armor, and are most often seen (iconographically speaking) in tournaments, though they do appear in battle from time to time as well (though how often they're used as artistic shorthand to identify the characters, I don't know for sure). These do not appear as an overgarment in non-armored contexts. This list only includes the surcoats with armorial decorations; there are plenty more that are solid-colored or with non-armorial decoration (i.e., fancy brocade patterns, etc.)

These are different from livery coats, which would be worn in battle by those fighting for a specific person. These also seem to be different in construction from heralds’ tabards.

For more information on design and construction, see Tournament Costume, and these links. I'd also recommend reading Janet Arnold's “The Jupon or Coat-Armour of the Black Prince in Canterbury Cathedral” in the 1993 Journal of the Church Monument Society, and also The Interrelationships of Costume and Armor (The Metropolitan Museum of Art Bulletin).