Green’s Dictionary of Slang

tray n.1

also dray, tre, trey
[Ital. tre, three]

1. [late 15C+] three, whether as a digit or a set of three; as v., to throw a three in dice.

2. [mid-19C] the male genitals, i.e. one penis plus two testicles.

3. [late 19C+] (also treemoon, treyer) a three-month or three-year prison sentence.

4. [1950s] £3.

5. [1950s+] (also treyer) $3.

6. [1960s+] (US black/drugs, also trey bag) a $3 packet of heroin.

7. [1970s+] (also trey bag) a $3 packet of marijuana.

8. [2010s] (UK Black/gang) a .357 revolver.

In compounds

tray-deuce (n.)

[1990s+] (US Und.) a .32 pistol.

In phrases

trey of knockers (n.) [the three balls hanging above such shops]

[1940s] (US black) a pawnbroker’s shop.