Green’s Dictionary of Slang

weasel (and stoat) n.

an overcoat.

1960, 1975		Wentworth & Flexner DAS 648/3: weasel and stoat – overcoat.
1971		J. Jones Rhy. Cockney Sl. 25: It’s a bit parky – I’ll put on me weasel.
1977		D. Powis Signs of Crime 207: Weasel (and stoat) Coat.
2001		M. Coles Bible in Cockney 25: Jacob gave a beautiful, decorated weasel to Joseph.