Green’s Dictionary of Slang

a housebreaker who employs a skeleton key.

1663		Caveat for Cutpurses in Bell Songs from the Dramatists (1861) 118: The Divel of hell in his trade is not worse / Then [sic] Gilter, and Diver, and cutter of purse.
1676		‘A Newgate ex-prisoner’ A Warning for House-Keepers 3: This Gilter is one that hath all sorts of Picklocks and false Keys to open any Locks both of Dores, Chests, Trunks and the like.