I've been trying to find details on this and I found three sources with one claiming Mid 60s, One said 1963 and another claimed 1961-62. Which year was the actual first year without radium? I did learn that Omega started putting Ts next to Swiss Made to signify the switch away from radium in the mid 1960s but sources claim they made radium free watches for a couple of years before incorporating the T.
I think 1962-5 was when they started phasing out radium. By 1965 I don't think they used any radium. Interested to hear what others have to say.
Interestingly I asked the same question last week and understand that the change from Radium to Tritium in the fifties seems to be model dependent. The Ts next to the Swiss Made signifies Tritium but it may be the case that a model doesn’t have the Ts and still be Tritium. I am not an expert in watches or for that matter vintage omega. What I have shared is information i’ve received from a respected member of the community. But happy to learn from other expert.
I previously read similar posts about Omega phasing out use of radium over several years beginning in 1962-63 and by 1965 only using tritium. I do have a 1963 Seamaster Deville with “Swiss Made” on the original dial and tritium lume used.
Just received an email response from OmegaEnthusiast.com who claimed that Omega stopped using radium by 1962. He did not provide a citation for that, however.
Omega phased out radium around 62 in favour of tritium due to safety issues. However, they were not bound by law to use Ts to signify that tritium was the energy source used until around mid 64. Therefore, some dials between 62-64 used tritium but had no T's. Equally some dials around 64 had the Ts retro fitted and that's why on certain dials from the period the Ts and Swiss Made aren't in perfect alignment.