Casting my own pocketwatch case - need pointers

Hey all; I’m a silversmith/jewellery designer, but also a bit of a nerd.

I wanted a “smart” pocketwatch - something that’s functional for me, so I can check my mail and get notifications, but also will look suitable when I’m wearing a suit.

So I’m building one with a 1.85” display & esp32s3 cpu board.

But the case is where I’m stuck. I can cast silver, and want to cast a half hunter design case - but the mechanical side of the case is where I’m struggling. Hinges are one thing, but does anyone have any pointers on how to design the release and catch mechanism, whether the back should be screw threaded or just a friction fit, what materials I should use (eg should a spring be steel, or can I cast it in brass or silver?)

Any tips would be most appreciated. A lot of stuff seems to be geared towards people using pre-bought parts and not how to make things from scratch.

Photo is just the first rev of my UI design and a god-awful “inspiration” idea done by AI.