Replacing the crystal in a Seiko V158-0AD0 watch

I have a Seiko V158-0AD0 which works very well, and I recently noticed the crystal was scratched more than the case… so a strong hint that it is an ordinary mineral glass crystal.

Searching the net, I could find that the Seiko part number for the original crystal is 310P03HN0 which indicates a diameter of 31.0mm but it does not have the thickness encoded simply. I could not find any articles giving the thickness of the part… so measurement was needed.

Above, the original crystal measures 1.6mm. A ‘standard' 1.5mm sapphire crystal should be just fine.

As this is a pretty new watch, and I have a 31.0×1.5mm sapphire crystal in stock, I replaced it on the spot, cleaned up with a bit of Rodico, some grease on the seal and reassembled the watch. I did not bother pressure testing it, it doesn't go swimming these days.

The 1.5mm crystal is thick enough to be just proud of the bezel.

Some hints:

  1. To release the stem look for the dimpled lever below the back plate with the stem fully inserted, depress it well and the stem comes out easily.
  2. Once the stem is out, place a case cushion over the movement, invert it and lift the case clear of the movement.
  3. The crystal presses out with the bezel in place.

I ordered a couple more sapphire crystals for stock, A$18 for two with shipping from Aliexpress.