Err...besides "_UnderLine_"..."-- or Hyphen" MAY be marked...
to indicate...the level of radioactivity of "Tritium"...such as,
"SWISS-T<25" ... "- T SWISS T -" ..."o T SWISS T o".
<br>
http://www.network54.com/Forum/207593/message/1234626200/%26quot%3BUnderLine-Tritium%26quot%3B+Theory.Illustrated+in+Japan+Vintag.+Rolex+collectors%27+magazine.%28scans%29
Best regards
Orchi.