red liner, n. — Green’s Dictionary of Slang

red liner n.

also red lioner

[when a boy was caught begging his name was noted down, with a red line drawn beneath it]

an officer of the Mendicity Society, a mid-Victorian society devoted to the suppression of street beggars.

1858		A. Mayhew Paved with Gold 105: They referred with delight to the great victory they had once gained over a ‘red liner’ — as the officers of the mendicity Society were termed.
1859, 1860		Hotten Dict. of Modern Sl. etc.
1864, 1867, 1870		Hotten Sl. Dict.
1873		Sl. Dict.