What does "T Swiss Made T" or
"Swiss T 25" 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 radio nuclides is authorized for timepieces: tritium
(3H) and promethium (147Pm). It is important to note that these radio nuclides
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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