This portrait is painted in enamel on metal. The advantage of enamel over traditional miniature painting (watercolour painted on vellum or on ivory) is that it does not fade when exposed to light. But the process of painting enamels is less free than miniature and is fraught with danger. The first colours to be laid on the metal support have to be the ones that need to be fired at the highest temperature. Then more colours are added and the enamel is re-fired. The process ends with the colours that need the lowest temperature. Such labour meant that it was an expensive option.

Enamel was first practised in England by a French goldsmith, Petitot, at the court of Charles I (ruled 1625-49). It was reintroduced about 1680 by a Swede, Charles Boit, and achieved wide popularity with the work of a German, Christian Friedrich Zincke. Both Boit and Zincke were goldsmiths by training. This miniature is by Charles Boit. It dates from about 1695 to 1700, at which time Boit was working in England. He fled the country in debt in 1714 and worked on the Continent for the rest of his career.

This enamel portrait is set in a locket punched with holes along the top and bottom. It was designed to be sewn onto a band of cloth, usually velvet, and worn on the wrist. Sadly, we do not know the identity of this gentleman in armour.