General Notes: Many have speculated about what the underline and/or exclamation point signify. Generally, they are thought to demarcate the transition from high radium content to lower radium (i.e. lower radiation) content and possibly the start of tritium use before the “T” designations became standardized in 1964. As with anything Rolex, all theories are based on correlation without direct evidence since the company releases little to no information. Instead of too much exposition on my part, I would direct you to a pair of excellent articles by Philipp of Rolex Passion Report here and here.
Serial Number Range: 687xxx-10xxxxx
Notes: Please note that this serial range is for dials with the underline and chapter ring and not for the underline without chapter ring. The chapter-ring underline dials seem to be almost exclusively on the Type 2 and 3 dials. I have seen a single Type 1 dial with an underline but have not had any to inspect closely to verify. If you are looking at a Type 1 dial with an underline – buy the seller and do your homework.
Serial Number Range: 62xxxx-990xxx
Notes: The chapter-ring with exclamation-point dials are most commonly found on the Type 2 dials. I have seen a few Type 3 dials with an exclamation but have yet to see a verified Type 1 dial with an exclamation. If you come across one, as above – buy the seller and do your homework.