Green’s Dictionary of Slang

tomato can n.

1. (US) the badge worn by a local or small-town police officer [the cheapness of its manufacture].

[[US]Ade Fables in Sl. (1902) 44: He went out to the Alley and found a Tomato Can that was not working, and he waited].
[US]Monteleone Criminal Sl. (rev. edn).

2. a second rate boxer [he is easily crushed].

[US]P. Hamill Flesh and Blood (1978) 174: I hope he ain’t a tomato can. [Ibid.] 178: They say he’s a tank artist, a tomato can, a guy who goes in the water for a few bucks, and that he was a good fighter once, a long time ago.
[US](con. 1954) ‘Jack Tunney’ Tomato Can Comeback [ebook] Tomato can being slang for a palooka who bled like a stuck pig; or got beat to a pulp.
T. Pluck on Twitter 16 Mar. [Internet] Fighting has certain a purity, if you’re mediocre you train harder, become a tomato can, or get a promoter who sets you up with cream puffs.

In compounds

tomato-can vag (n.) (also can moocher, tomato can stiff, tomato-can tramp)

(US tramp) the lowest rank of vagrant.

[US]J. Flynt Tramping with Tramps 119: If he is a victim of liquor, and lives long enough, he is sure to end as a tomato-can tramp. [Ibid.] 398: Tomato-Can Vag [...] a tramp of the lowest order, who drains the dregs of a beer barrel into an empty tomato-can and drinks them.
[US]St Louis Republican (MO) 30 Aug. 52/2: I don’t want to see you turn out a tomato can vag. You’re the flyest kid I ever trained.
[US]P. & T. Casey Gay-cat 304: Tomato-Can Vag — the hobo outcast. So called because he empties beer-barrel dregs into a tomato-can and drinks them.
[US]Irwin Amer. Tramp and Und. Sl. 46: Can Moocher.– A tramp or bum, filthy, lost to hope and ambition and often demented, an exile from everything worth while. Originally the tomato can was used as a container into which were drained the dregs from beer kegs outside of saloons ; later the same receptacle came to be used as a catch-all for begged or salvaged food. [Ibid.] 189: Tomato Can Stiff.– One of the lowest bums, looked down upon by those of the fraternity who are as yet able to hold their own.
[UK]F. Jennings Tramping with Tramps 212: Tomato Can Tramps – those who curl up anywhere.
[US]Monteleone Criminal Sl. (rev. edn).
[US]Goldin et al. DAUL 224/2: Tomato can vag. A hobo, especially one with enough experience to cook good mulligan stew in a gallon tomato can over a bonfire.