How to restore the Omega Seamaster 300 bezel-insert
First, let me say that I do not ordinarily undertake home restoration of expensive vintage military watches. This was a case of
mother-of-invention, though the method was first described to me by Hyunsuk; either he or his legendary watchmaker was the
inventor. Since so many 300 bezels have inserts in such wretched shape, owing to a very undurable design, and since the result is
really quite remarkably nice (wish I had a scanner) I'm going to tell you exactly how to do it.
You will need: #2 round sable modeller's brush, a "fine"-grade Premium Sanding Stick, pack of Testor's plastic-sanding sheets in
finest grades, plastic enamel in matte black and matte desert tan (Humbrol or Testor's), two sewing needles.
1. Examine insert with loup, looking for radial cracks (cracks across the width of the insert, radiating, as it were, from the center of
the dial). If you spot any (and they may be on the underside of the insert) you haven't a hope in hell and need either a new bezel
and insert or a new insert. If you see a crack, abandon the project! Your insert will come out in useless pieces!
2. Pray. Insert one of the needles into the loosest point you can find around the outside edge of the insert. Gently lever it back and
up. The insert is 1mm thick and slightly flexible. When you've levered the insert up sufficiently, stick the second needle beneath the
insert to keep it from snapping back into place. Fiddle with the second needle. The insert is a press-fit, and will loosen and come off,
probably leaving 40% of its water-damaged paint and tritium on the track in the bezel.
3. Clean track in bezel with a few drops of paint thinner and a stiff toothbrush, removing all residue.
4. Wash the insert under warm water, removing tritium and loose paint. Scrub gently with a soft tooth brush. Dry.
5. Place the insert face-down on a piece of chamois on a hard flat surface. Sand off the remaining black paint with the sanding stick,
being careful not to remove plastic. (Do not sand edges of insert, as this would affect press-fit for reassembly.) Wash again to
remove black sanding-dust. Dry.
6. Use one of the needles to pick out any bits of black that are stuck in the numeral and five-minute depressions. (The minute
chapters are, in my experience, almost always okay; they are filled with tough white paint and stay that way. Good for them.) Wash
and stiff toothbrush again.
7. Fold the next-to-finest sanding sheet around the sanding stick and sand back of insert. Follow with finest. A smooth, translucent,
slightly matte surface is perferable; you don't need to polish the back to high shine. Wash and dry.
8. Thoroughly mix sand-colored paint. Apply to numeral and five-minute depressions, filling them. Slopover onto back is okay; in
fact, unavoidable. Let dry. Repeat. Let dry 24 hours.
9. Using sanding stick and sheets, sand tan slopover off back of insert. Wash. Dry.
10. Mix matte black. Paint entire back of insert with matte black. Let dry 24 hours.
11. Insert insert into bezel. Press fit. Presto!
Successful result is virtually indistinguishable from original. Almost all 300 inserts have inactive tritium faded to one or another degree
Purists may frown at this, but I regard it as being closer to the original than any redial; you are refilling precision photo-etched
grooves, so each numeral and chapter is exactly as Omega meant it. Ironically, these paints are waterproof, unlike the ones Omega
used. That said, I don't want to have to do this again, ever, and it's put an end to my seemingly insatiable appetite for 300s. I will
keep my mint RN 300 and keep it very VERY dry, thank you.
Hope this will help somebody with a flaking but intact insert and the requisite motor skills. If you've got the right kind of nerves, it's
actually very satisfying.