Green’s Dictionary of Slang

1. (also Gregory) the neck.

1967		‘Whisper All Aussie Dict.’ in Kings Cross Whisper (Sydney) xxxv 6/1: gregory peck: Neck.
1968		J. Alard He who Shoots Last 153: In his hurry ta git outa da bath, da poor coot slips on da Bob Hope and breaks his gregory.
1975		Bulletin (Sydney) 26 Apr. 46: Rhyming slang did filter through into the idiom. But the knock-abouts quickly turned most of the phrases into shortened versions – Gregory (short for Gregory Peck: neck): the Rory (short for Rory O’More: the door) [...].
1983		J. Byrell (con. 1959) Up the Cross 10: ‘Awful reached out and got him by the gregory’.
1985		J. Sullivan ‘Hole in One’ Only Fools and Horses [TV script] All you can think about is your rotten Gregory!
2000		N. Griffiths Grits 467: A whole fuckin pharmacy straight dahn is gregory.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 81/2: Gregory Peck n. the neck.
2005		P. Howard Curious Incident of the Dog in the Nightdress 1: Another JD disappears down the old Gregory.
2018		Twitter 19 June 🌐 I AM FAAKIN HANK MARVIN. I CANT WAIT TO GET THESE SAMMICHES DOWN ME GREGORY.

2. a cheque.

1981		P. Wright Cockney Dialect and Sl. 104: Gregory Peck ‘cheque’.
2003		Guardian Weekend 22 Feb. 7: My Hammersmith window-cleaner who would insist on ‘bees and honey’ (money) rather than a ‘Gregory Peck’ (cheque).
2013		K. Sampson Killing Pool 66: ‘What can he do?’ ‘Whatever we want. Dollars. Deutschmarks. Gregories...’.

3. in pl., spectacles, glasses [= specs n. (1)].

2001

G. Coughlan Everyday Eng. and Sl. 🌐 gregory pecks : specs.