Protection of non-conforming uses. Non-conforming uses are allowed to continue operation in the same manner and extent of the non-conformity present at the time of adoption of the zoning bylaw which made the use non-conforming. This section shall not apply to billboards, signs, and other advertising devices subject to the provisions of MGL Chapter 93, Sections 29 through 33, inclusive, Chapter 93D or to adult bookstores, adult motion picture theaters, adult paraphernalia shops or adult video stores subject to the provisions of MGL Chapter 40A, Section 9A.