Rolex Swiss T<25 (Swiss t 25) Complete Guide
If you look closely at the bottom of a Rolex dial at 6 o’clock, you will be able to find a printing there. Depending on when the watch was made, the printing may vary. And the different printings also have different meanings.
If you have seen a dial that has the printing ”swiss t 25”, or more correctly ”Swiss T<25”, you may wonder what this means.
What does Swiss T<25 mean?
When you see the printing Swiss T<25 on a Rolex watch, it first means that the watch is Swiss made. Furthermore, the T stands for tritium, which tells us that this is the material used for the watch’s luminosity. And lastly, the <25 is the indication of how much tritium the watch emits. In this case, it means that it emits less than 925 MBq (25 mCi). 
This marking can be seen on Rolex watches which use tritium, and as such, by looking at this printing, you will be able to get an idea of when the watch was made. This dial marking was used between 1960 and 1998, but note that with Rolex, things are not as clear-cut as you may wish, due to their secretive way of conducting business. This means that deviations may apply from these years.
An interesting side note about this, however, is that some late marked service that has the print “Swiss T<25” on them has actually proven to be Luminova and not tritium, which the printing is supposed to indicate.
