(1) Apparatus license plates, as provided for in chapter 17.21 RCW, shall be attached to and prominently displayed on the apparatus for which they have been issued: Provided that an apparatus license plate may be affixed to a vehicle which contains the particular apparatus. Attached plates shall be clearly visible and in a location easily accessible for inspection by the department.

(2) Each vehicle involved in the operations of a certified commercial ground application business, which does not prominently display a department issued apparatus license plate on its exterior or on the specific apparatus when that apparatus is exteriorly visible, shall be required to have a department issued sticker affixed to the lower left side of the windshield.