The Rolex Submariner reference 5508 is a historically important model for multiple reasons, but perhaps its most notable reason is it the last reference lacking the use of crown guards to protect the crown against incidental impact. Another notable reason is the use of a smaller crown. A departure was made on the bezel from the red painted triangle for a silver triangle which surrounds the lume pip, a design which is still seen on modern Submariners to this day. We also see the use of a different luminant material using a lower amount of radium, which is represented by the small dot at the six o’clock under the lume plot but right above the minutes track. This little flourish has been given the nickname of an “exclamation point”, truly a surprising standout from most other Submariner references. Shop Rolex Submariner Collection