Cal. Code Regs. tit. 25, § 3038
(a) Each factory-built dwelling, dwelling unit, individual dwelling room or combination thereof shall have attached thereto a permanent unit serial number. The unit serial number shall be visible throughout all phases of construction, including installation at the site.
(2) Unit serial numbers for factory-built housing consisting of two or more units shall, for the purpose of identifying each unit as part of a specific group, conform to the format of:
x-y (z)
where:
x is a serial number common to each unit in the group,
y is a number or letter identifying a specific unit within the group, i.e. 1, 2, 3, or A, B, C, etc.,
z is an optional number denoting the total number of units in the group.
An example of unit serial numbers for factory-built housing consisting of two units would be 1000-1(2) and 1000-2(2).
Unit serial numbers shall consist of at least the following:
Note: Authority cited: Sections 17003.5 and 19990, Health and Safety Code. Reference: Section 19990, Health and Safety Code.
1. Amendment of subsection (a) filed 11-18-86; effective upon filing (Register 86, No. 47).