Green’s Dictionary of Slang

lamper n.

[lamp v.1 (2)]

(US/W.I.) a confidence trickster.

[US]S.F. Chron. 6 June 11/5: De lampers stood ’round till dey got wise to de joint, an’ dey didn’t do a t’ing but queer me marks.
[WI]cited in Cassidy & LePage Dict. Jam. Eng. (1980).