Have the backs of the dials been checked for marks to show if the supplier is consistent between G/G and G/B dials? Heuer used Singer for quite a few dials but it's apparent that they used other companies at times too.

Maybe the contract would go to whoever could nail the metallic blue finish of the 1133 B, and the G dials each company supplied were different from each other.

Maybe the G/B was an experiment that was reverted, given that we seem to have G/G dials topping and tailing the list of serial numbers.

Unlike some dials (the blue through violet fades of 1553 dials, for example), the darker registers on these seem intentional so there should be some rhyme and reason behind it - let's see if that reason is still discoverable after so many years!