I've never noticed this before, maybe it's old news.. but thought I'd share, in case anyone else didn't know.
I only spotted it this week. Anyway, there are two types of dial.. the difference is in the hour batons. I dug through the catalogues, and:

- The early 72-74ish models have polished batons with a black strip, and small lume plots at the end.
- The later, circa post 74 models (going by the catalogues) have the painted upper surface of the batons, with a lume strip in-between.

I don't know when the baton design changed, but somewhere between 74 and 77 going by the catalogues. I presume that same may apply to the other dial designs in the 11630 range - silver and white maybe. I wonder if the Cal. 15 were the same too?

This is mine - earlier style..

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and here is an example from the OTD picture archives..

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72 catalogue:

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74 catalogue, same as above:

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change of baton, shown in the 77 catalogue..

Stewart
- Heuerville