1. There are exempted from the taxes imposed by this chapter the gross receipts from the sale of, and the storage, use or other consumption in a county of, tangible personal property used for the performance of a contract on public works executed prior to July 1, 1967.
2. There are exempted from the additional taxes imposed by amendment to this chapter the gross receipts from the sale of, and the storage, use or other consumption in a county of, tangible personal property used for the performance of a contract on public works which was executed prior to May 1, 1981, or for which a binding bid was submitted before that date if the bid was afterward accepted.