Green’s Dictionary of Slang

(UK Und.) newly coined money.

1859		Matsell Vocabulum.
1882		Dly Dispatch (Richmond, VA) 1 Nov. 3/3: [Villains] have lots of names for money, such as [...] ‘new light’.
1895		C. Crowe Aus. Sl. Dict. 52: New Light, new money.