Nothing in this article shall be construed to require the payment of a tax by any person for any period prior to January 1, 1977 by reason of such person having engaged in business as a steamship agent; for any period prior to January 1, 1980 by reason of such person having engaged in business as a custom house broker; for any period prior to January 1, 1981 by reason of such person having engaged in business as a stevedore; or for any period prior to January 1, 1984 by reason of such person having engaged in business as a tugboat or barge operator. (Amended by Ord. No. 159,314, Eff. 9/29/84.)