the head-piece or canopy of the bed; also a vulgar term for a sixpenny piece, all over England.
·noun A headpiece; a helmet. II. Tester ·noun A flat canopy, as over a pulpit or tomb. III. Tester...
Webster's Dictionary of the English Language
A sixpence: from TESTON, a coin with a head on it. ...
Dictionary of The Vulgar Tongue by Francis Grose