Any sign lawfully in existence prior to the effective date of this section[1] may be continued, provided that the same shall be regularly maintained and kept in good repair. However, no change in lettering, content, size, construction, location or lighting of such sign shall be permitted except by approval of the land use board.

No nonconforming sign may be enlarged or altered in such a way as to increase its nonconformity. All nonconforming signs shall be removed or shall be altered to conform to the provisions of this section when any such sign is changed or modified in either in shape, size, illumination or structure. Should any nonconforming sign be damaged by any means to an extent of more than 50% of either its replacement cost or structural elements at time of damage, such sign shall not be reconstructed except in conformity with the provisions of this section.