Help what is what on this 5512 1959? expert advice needed

[EONwatches]

Hi guys, new here, happy to be here!

got offered this one but i am totally lost on it. Need some expert advice, my questions:

- serial dates to 1959 but engraving of serial and ref are weird? or this is possible in this time frame? is this a service case?
- Meter first dial looks all good but is later right?
- caseback looks correct?
- movement looks correct?
- bezel correct for 1959?

in general is the questions, what is what? i am lost, been searching for hours now