'T Swiss Made T' or 'Swiss T 25' : What does it mean ?

'T Swiss Made T' or 'Swiss T 25' : What does it mean ?

In order for timepieces to be read in the dark, a radio luminescent material is laid on the dial indexes and hands.
According to ISO 3157 Standard, only the use of the following radionuclide is authorized for timepieces: tritium (3H) and promethium (147Pm). It is important to specify that these radionuclide emit a radiation of low energy, perfectly confined by the watch case and glass; they may under no circumstances threaten the health of the watch user.
ISO 3157 Standard allows an optional marking for timepieces emitting less than a certain value. The marking may be made on the dial as follows:

deposits activated by tritium : T
deposits activated by promethium : Pm

On the other hand, timepieces with a higher value, such as divers' watches, must be marked as follows:

deposits activated by tritium : T 25
deposits activated by promethium : Pm 0,5

The indication "T Swiss made T" means that the watch is Swiss and contains a certain quantity of tritium that emits less than 227 MBq (7,5 mCi). The indication "Swiss T 25" means that the watch is Swiss and contains a certain quantity of tritium that emits less than 925 MBq (25 mCi).




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