Green’s Dictionary of Slang

tomato can n.

1. [1920s–40s] (US) the badge worn by a local or small-town police officer [the cheapness of its manufacture].

2. [1970s] a second rate boxer [he is easily crushed].

In compounds

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

[late 19C–1940s] (US tramp) the lowest rank of vagrant.