Green’s Dictionary of Slang

1. orig. naval, a prison [= tank n.² (1)].

1962		J. Wynnum Tar Dust 76: ‘An’ look lively about it or I’ll slap you in the rattle for feigning sickness’.
1984		(con. WW2) T. Jones Heart of Oak [ebook] I’d had a knee trembler with a bird outside the Heffelent and got a nap hand ... and I went adrift ‘cos I didn’t want to be in the rattle for the next bleeding ten years.

2. a bank.

1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.
1998		R. Puxley Fresh Rabbit.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.