Green’s Dictionary of Slang

Black Jack n.

[the nickname of Sir John Sylvester, the Common Sergeant of London c. 1810]

the Recorder of London.

1811		Lex. Balatronicum n.p.: Black Jack. A nick name given to the Recorder by the Thieves.
1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc.