Section 6. Every motor vehicle or trailer registered under this chapter when operated in or on any way in this commonwealth shall have its register number displayed conspicuously thereon by the number plates furnished by the registrar in accordance with section two or five or by temporary number plates authorized by the registrar as hereinafter provided, one number plate to be attached at the front and one at the rear of said motor vehicle, and one number plate to be attached at the rear of said trailer, but if the registrar issues but one number plate it shall be attached to the rear of the vehicle so that it shall always be plainly visible. The said number plates shall be kept clean with the numbers legible and shall not be obscured in any manner by the installation of any device obscuring said numbers, and during the period when the vehicle or trailer is required to display lights the rear register number shall be illuminated so as to be plainly visible at a distance of sixty feet. No number plates other than such as are procured from the registrar or such as may be authorized by him for temporary use, except as provided in section three, shall be displayed on any motor vehicle or trailer so operated; provided, that a motor vehicle or trailer which by reason of its interstate operation is registered in this commonwealth and elsewhere may display the register number plates of this and any other state or country in which it is registered, if, while being operated on the ways of this commonwealth, the number plates furnished by the registrar, or temporary number plates authorized by him as hereinafter provided, are displayed as required hereby. If any number plate supplied by the registrar is lost or mutilated or if the register number thereon becomes illegible, the owner or person in control of the vehicle for which said number plate was furnished shall make application for a new number plate, and thereupon the registrar shall issue to such applicant a permit allowing him to place a temporary number plate bearing his register number on said vehicle until a number plate of the regular design is made and delivered to said applicant; provided, that all such temporary number plates and the register numbers thereon shall conform to the regular number plates and be displayed as nearly as may be as herein provided for said regular number plates. Any motor vehicle or trailer may, if duly registered, be operated, pushed, drawn or towed or remain upon any way between the hours of twelve o'clock noon on the date on which its registration expires and twelve o'clock noon on the following day, if the following day is the first day of the new registration period, and if such vehicle or trailer displays its register number for either registration period as otherwise required by this section.