California Code, Penal Code - PEN § 648a

(b)(1) The slug or token shall either be clearly identified with the name and location of the establishment from which it originates on at least one side or shall contain an identifying mark or logo that clearly indicates the identity of the manufacturer.

(2) The slug or token shall not be within any of the following diameter ranges in inches:

(3) The slug or token shall not be manufactured from a three-layered material consisting of a copper-nickel alloy clad on both sides of a pure core, nor from a copper-based material except if the total of zinc, nickel, aluminum, magnesium, and other alloying materials is at least 20 percent of the token's weight.

(4) The slug or token shall not possess sufficient magnetic properties so as to be accepted by a coin mechanism.

(5) The design on the slug or token shall not resemble any current or past foreign or United States coinage.

(6) Establishments using these slugs or tokens shall prominently and conspicuously post signs on their premises notifying patrons that federal law prohibits the use of the slugs or tokens outside the premises for any monetary purpose.

(7) The issuing establishment shall not accept slugs or tokens as payment for any goods or services offered by the establishment with the exception of the specific use for which the slugs or tokens were designed.