Green’s Dictionary of Slang

weasel (and stoat) n.

[rhy. sl. = coat]

an overcoat.

[US]Wentworth & Flexner DAS 648/3: weasel and stoat – overcoat.
[UK]J. Jones Rhy. Cockney Sl. 25: It’s a bit parky – I’ll put on me weasel.
[UK]D. Powis Signs of Crime 207: Weasel (and stoat) Coat.
[UK]M. Coles Bible in Cockney 25: Jacob gave a beautiful, decorated weasel to Joseph.