A sign lawfully existing at the effective date of the adoption or amendment of this title but which would be prohibited under the terms of this title or amendment to this title shall be deemed nonconforming, and may continue if not altered, rebuilt, enlarged, extended, or relocated; provided, that if such nonconforming sign is located in an R district, such sign shall be removed within two (2) years from the effective date of this title or amendment thereof. (Ord., 3-8-1971)