This stamp was issued for collectors.  It was first sold without an overprint but was later hand-stamped “cancelled,” to prevent it from being used for postage.  This practice of selling stamps specifically for philatelic reasons was common in the early days of the Hawaiian postal system.  These stamps were sold only at the Honolulu post office, and usually for face value. 

Why some Hawaii stamps were
created just for stamp collectors...

There was a great demand for Hawaii stamps from collectors in the United States.  Hawaii’s connection to the U.S. was quite strong, and it was evident to many people that Hawaii would eventually become a U.S. state.  This made the stamps popular in the U.S.  But the small number of Hawaii stamps issued for postal purposes could not possibly supply demand.  Postal authorities created “official imitations” and reproductions, thereby collecting a sizable profit on stamps that would never frank mail.