Why does Tudor lume often look dirty?

[ravenhome777]

Has anyone noticed that vintage Tudor lume from 7928 timeframe often looks dirty?

For example:
https://postimg.cc/D849QNZD

https://postimg.cc/mckNMvZ1

Whereas Rolex Submariner lume from this era generally looks clean and nicely patined to a cream color:

https://ibb.co/7vMV0kW

This dirt accumulation isn't the rule. I have seen nice creamy lume examples of Tudors, but I do see it often. I was wondering if perhaps Rolex could have been using a slightly inferior lume recipe for Tudors during this period. Purely speculation, but just curious if that could have been the case.