Green’s Dictionary of Slang

tower n.²

(UK Und.) clipped money.

c.1698		implied in go around the tower
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1809		G. Andrewes Dict. Sl. and Cant.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1835		G. Kent Modern Flash Dict.
1848		Flash Dict. in Sinks of London Laid Open.

In phrases

go around the tower (v.) (also go round…) [play on the Tower of London, where money was minted, and a tour around the circumference of the coin]

(UK Und.) to clip money.

c.1698		B.E. Dict. Canting Crew n.p.: They have been round the Tower with it, c. that Piece of Money has been Clipt.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.