What does this mean on my sub?

[Tommer]

Swiss-t<25

[tonelar]

less than 25 milicuries of radiation from the tritium used to make th dial and hands glow.
see that edit button under your post? you can hit that to go back and make changes...

[Tommer]

milicuries?

[mike]

Your sub has a tritium dial. Prior to circa 1998 Rolex used tritium as an exciting agent to cause the phosphors in the paint matrix to glow.
Tritium is a mildly radioactive substance (beta). T<25 means the tritium emites(emited less that 25 milicuries of radition.
Tritium has a half-life of about 12.5 years. After 1998, due to new regulations Rolex and other brands switched to luminova, a non radioactive compound. Luminova needs to be "charged" by light to glow.

[tonelar]

Originally Posted by Tommer

milicuries?

you know.. a fairly common measure of radioactivity in the lower end of the spectrum...

25 milicuries of Beta waves won't even radiate past the watch crystal.

[Erix]

Originally Posted by Tommer

Swiss-t<25

Here is an extract from a good site for FAQ on swiss watches: http://www.fhs.ch/en/faq.php

"T Swiss Made T" or "Swiss T 25" : what does it mean ?

In order for timepieces to be read in the dark, a luminescent material is laid on the dial indexes and hands. Generally speaking, the emission of light is either of photoluminescent type (determined by a exciting luminous radiation) or of radioluminescent type (determined by the radioactivity of the material).

Timepieces featuring radioluminescent emission are mostly designed for very specific uses : military watches, professional divers watches, etc. In this case, the use of radioactive material is strictly defined by ISO 3157 Standard which allows only two types of radionucleides : tritium (3H) and promethium (147 Pm). It is important to specify that these radionucleides emit a radiation of low energy.

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).

Most of the Swiss watches use a light emission of photoluminescent type. Some of them bear the optional marking "L Swiss Made L" to indicate it.

[nko51]

It tells me that it is not a post 1985 model dial.

[Prince]

Originally Posted by nko51

It tells me that it is not a post 1985 model dial.

What do you mean? All of my watches are mid to late 1995 and they all have the "Swiss-T <25" or the "T Swiss Made T" on them.

[tonelar]

oh my... i actually think it was 1998 when ROlex made the switch. Although a few Swisst<25 dials were actually used after this date, only with luminova on them (as opposed to the tritium formula).

[Prince]

Originally Posted by tonelar

oh my... i actually think it was 1998 when ROlex made the switch. Although a few Swisst<25 dials were actually used after this date, only with luminova on them (as opposed to the tritium formula).

Thanks, Tony. I thought that was the case. In fact, Mike states such in post #4 above.