SUPERTAX n.
addition to the usual or normal tax; specif., in the United Kingdom, an income tax of sixpence for every pound in addition to the normal income tax of one shilling and twopence for every pound, imposed, by the Finance Act of 1909-1910 (c. 8, ss 66, 72), on the amount by which the income of any person exceeds £3,000 w…
TESTER n.
An old French silver coin, originally of the value of about eighteen pence, subsequently reduced to ninepence, and later to sixpence, sterling. Hence, in modern English slang, a sixpence; -- often contracted to tizzy. Called also teston. Shak.