Question: Valentine Trem: What are the four internal potis for? How to adjust the bridge?

Hi,
I got a new Valentine Trem! It’s a awsome guitar and I’m sure we are getting old together! 🙂
But I have two questions:
1. What are the four internal trim potis for?
2. How to adjust that bridge? There is that ashtrayish thing, which I can not take off. How do I get access to the screws of the riders? :confused: That bridge is completely new to me…
thanks