Watch SafeHorology glossaryDefined term / radium
Radium
The radioactive luminous material used on watch dials and hands from the early 1900s until the 1960s, when safer tritium replaced it.
Authentication note
Why this detail matters.
Radium marks the earliest lume era, so its presence must agree with the watch's production years and dial text. Genuine radium lume no longer glows, though it remains radioactive and detectable with instruments. Relumed vintage dials that glow brightly where radium should sit inert are a common originality problem, distinct from fakery but priced very differently from untouched examples.