Green’s Dictionary of Slang

one pound sterling.

1902		Bulletin (Sydney) 9 Aug. 35/2: [A]t the finish it clearly revealed itself as ‘send six squids.’ All else was mystical.
1997		N. Barlay Curvy Lovebox 56: Here’s a coupla squids for the box.
2005		P. Howard Curious Incident of the Dog in the Nightdress 62: He [...] reckons Hugo Boss is going to give him a million squids for [it].
2012		J. Fagan Panopticon (2013) 205: One guy paid me two hundred squaids tae piss on him.
2017		Twitter 15 Dec. 🌐 It’s gotta feel strange seeing copies of your old work changing hands for more squids than you probably got paid, back in the day.