A ''Diptych'' (as seen previously) was a form of Religious Art associated with Altar Pieces. These were hinged Panels with either painted or carved religious imagery. The ''Wilton Diptych'' was painted in the 14th Century for King Richard II of England (who was in fact ''painted'' into The Diptych).
Several English Kings prior to Richard are also portrayed, in the company of various Saints and Religious figures from The Bible. The Dipytch was constructed from Oak Panels which were hinged. This allowed for them to be ''closed'' when not in use (viewing). Fine Gold plating was used as the Medium Field, to which was applied pigment (some of which was mixed with crushed precious metal and gems, commonly done with some works of this nature).
While ''Wilton'' is NOT the name of it's painter and builder (which today is still unknown), the style is similar to various Master Painters from Wilton (Northern England) – hence it's identification. The Diptych is currently in possession of The National Gallery in London, England.