Green’s Dictionary of Slang

burnt (cinder) n.

a window.

1923		Smith’s Wkly (Sydney) 11 Aug. 15/2: A jimmy scientifically applied will open any red-`hot cinder.
1925		(con. WWI) Fraser & Gibbons Soldier and Sailor Words 40: Burnt Cinders; Windows (Rhyming Slang).
1930		(con. 1910–20s) D. Mackenzie Hell’s Kitchen 118: Burnt cinder ... a window.
1935		A.J. Pollock Und. Speaks n.p.: Red hot cinder, a window.
1935		Thieves Slang ms list from District Police Training Centre, Ryton-on-Dunsmore, Warwicks 2: Burning cinder: Window.
1950		P. Hoskins No Hiding Place! 190/1: Cinder. (Burnt cinder.) Window.
1953		J. Phelan Underworld 26: [of an office] ‘Wants a screwsman to do his gaff, stick three burnts, and lolly the peter’.
1962		F. Norman Guntz 6: The geezer behind the burnt gave me a dodgey look.
1969		S.T. Kendall Up the Frog 13: The ol’ currant bun was a-shinin’ through the burnt cinder.
1978		F. Norman Dead Butler Caper 103: That butler geezer captured ’im bang to rights just as ’e climbed in the burnt.
1979		F. Norman Too Many Crooks Spoil the Caper 2: I ’ad it away out the burnt cinder.
1981		P. Wright Cockney Dialect and Sl. 103: burnt cinders ‘windows’.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.

In compounds

stiff-burnt (n.)

(UK und.) a plate-glass window (as used by a shop).

1953

J. Phelan Underworld 89: ‘[H]e were the best man for miles on a stiff-burnt’.