Cal. Pub. Res. Code § 18015

(a) All rigid plastic bottles and rigid plastic containers sold in California on and after January 1, 1992, shall be labeled with a code which indicates the resin used to produce the rigid plastic bottle or rigid plastic container. Rigid plastic bottles or rigid plastic containers with labels and basecups of a different material shall be coded by their basic material. The code shall consist of a number placed inside a triangle, and letters placed below the triangle. The triangle shall be equilateral, formed by three arrows with the apex of each point of the triangle at the midpoint of each arrow, rounded with a short radius. The pointer (arrowhead) of each arrow shall be at the midpoint of each side of the triangle with a short gap separating the pointer from the base of the adjacent arrow. The triangle, formed by the three arrows curved at their midpoints shall depict a clockwise path around the code number. The numbers and letters used shall be as follows:

(c) On and after January 1, 1989, the Division of Recycling of the Department of Conservation shall maintain a list of abbreviations used on labels pursuant to subdivision (a) and shall provide a copy of that list to any person upon request.