Hi Tom,
Here’s my theory on Peter’s pair that you showed. The middle example is a pure dress watch (I doubt that the crown is original), and as such, relatively fine print was used on the dial. The one on the right is a more bold design, in that there are black inserts (onyx, perhaps) in three of the hour markers. A heavier font actually works well as a compliment to the inserts, and (this is the most speculative part), I have seen a similar dial design (albeit in a steel case) in which there was luminous material, rather than inserts placed in the hour markers. So, perhaps there was one basic dial used for both models, and the “T” was included to denote tritium on those models that actually included the material.
Sometimes we collectors need to remind ourselves that few, if any working for these manufacturers were thinking about how collectors might obsess over details 50 years hence. If there was no tritium on some of the models on which “T” appeared on the dial, so what?
Regards,
Tony