What baseball team's hat does Magnum wear in Magnum, P.I.?

On December 11, 1980, the world was introduced to lovable, laid-back former Navy Seal turned private investigator Thomas Magnum when Magnum, P.I. premiered on CBS.

It was the breakout role for one Tom Selleck, whose mustache may just be the most iconic of the 1980s. He plays a P.I. who lives a carefree life, apparently for free, on an estate owned by the mysterious Robin Masters, and cared for by Jonathan Quayle Higgins III and his two Dobermans.

The show ran for 8 seasons and 162 episodes and enjoyed perenially high ratings throughout its original run.

Oh yeah, and it has one of the most badass TV theme songs in history:

Throughout the show's run, Magnum became known for his many signature character traits, including button-up Aloha shirts and running up neverending tabs. He was also often spotted in one of two baseball caps, one from the Marine Corps and one for this baseball team.

Which team was it? And yeah, we're only talking original run here, but you probably already knew that.