tester | Dictionary of The Vulgar Tongue by Francis Grose

Tester
·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
tester
the head-piece or canopy of the bed; also a vulgar term for a sixpenny piece, all over England. ...

A glossary of provincial and local words used in England by Francis Grose