The registration provisions of this article shall not apply to any of the following:
(a)
Any trailer coach which is driven or moved upon a highway in any of the following circumstances:
(1)
In conformance with the provisions of this code relating to dealers, manufacturers, transporters, or nonresidents.
(2)
Under a temporary permit issued by the department as authorized by Section 4156.
(3)
Under a one-trip permit issued by the department as authorized by Section 4003 when such permit is issued to a nonresident.
(b)
Any unoccupied trailer coach which is part of an inventory of trailer coaches held for sale by a manufacturer or dealer in the course of his business.