Green’s Dictionary of Slang

tin plate n.

[rhy. sl. = mate n. (1)]

a friend.

[Aus]G.H. Lawson Dict. of Aus. Words And Terms 🌐 TIN-PLATE — A mate.
[UK](con. WWI) A.E. Strong in Partridge Sl. To-day and Yesterday (1933) 287: Group. Where’s your Tin Plate? I suppose he has been making it too hot lately and they have kept him in the line.
[UK]J. Franklyn Dict. of Rhy. Sl.
[UK]Dodson & Saczek Dict. of Cockney Rhy. Sl.
[UK]R. Puxley Cockney Rabbit.