Any non-conforming sign damaged to the extent of more than sixty percent (60%) of its reconstruction value, exclusive of the foundations, at the time of damage by fire, explosion, war, riot or act of God, shall not be restored or reconstructed as before such happening. However, if less than sixty percent (60%) of such a sign is damaged above the foundation, it may be restored or reconstructed, provided that such restoration or reconstruction is done within four (4) months of such happening, and is done with like or similar materials and size.