Has anyone seen a Big Blue dial and 9 o'clock subdial turns so.... yellow/gold? Is this a common color when the blue dial ages? I've seen these turn tropical brown but this? Notice the arrow on the subdial is blue rather than typical red. What gives?

 

It looks like it was stripped to the brass and painted with lume. Just a guess.

 

Yet maintained the integrity of the text and markers?

 

Could be a rare gold plated "Big Blue"?

 

Fairly typical of these blue Omega dials to turn gold although usually not as completely as seen here, this phenomenon is not limited to the Big Blue dials.

 

This is a truly interesting example.

This is just the wrong part IMO, it should go with a silver-dialed 1040. The rest is curious...

Prior to this example the most extreme case of a blue dial turning gold I've seen is this Mark III:

As you can see, the white text and markers retained their integrity on this Mark III, but the gold is much more uneven than on the OP dial.

What is really interesting to me about the OP dial is that the vertical grain of the dial is still intact. I confess I know nothing about how that effect is created in the first place, but I'm surprised that the loss of the blue color hasn't affected the grain.

Anyway, I'm curious to know how this color change happens. Most sellers describe them as being "tropical" and chalk it up to a combination of humidity and sunlight. Water ingress has also been suspected. But I wonder if there's a way of artificially treating these (chemicals or baking in an oven?) to accelerate the process, which creates these extreme examples.

 

It's my understanding that the original owner of the watch pulled this dial off of his Big Blue when it had already turned this color. Perhaps it's a paint defect like the cream colored Rolex 16550 explorer?

 

I think defect is a good word for it, as it only seems to happen on the blue dials and not the silver, gold, brown, or black dialed 1040 dials.