Green’s Dictionary of Slang

mint adj.

also mintox, mont, real mint
[SE mint, unblemished]

(Can./US/UK teen) a general term of thorough approval.

[Aus]C. Bowles G’DAY 99: If something is [...] very good, it’s magic, top stuf, or mint, but often beaut or ripper.
[US]J. Doyle College Sl. Dict. 🌐 mint [CMU] really cool.
Online Sl. Dict. 🌐 mint adj 1. attractive, usually a male. (‘That guy is mint.’).
[UK]Guardian Rev. 3 Nov. 17: Purely Belter means more brilliant than ‘cushdy’ or ‘mint’; it means, as it were, doubleplusgood.
OnLine Dict. of Playground Sl. 🌐 mint, mintox, mont adj. excellent.
OnLine Dict. of Playground Sl. 🌐 real mint n. great, good to look at, fine looking.
[NZ] McGill Reed Dict. of N.Z. Sl.
[UK]R. Milward Apples (2023) 29: Everyone looked mint without the crap baggy [school] shirts and that.