Old electrical installation - can the age be determined?

Well, so far it looks okay. I'll have an electrician take a look. He will open it briefly and check it out. If everything is 3-core, it can often be expanded. And yes, 50 years ago, an installation like the one pictured would already be considered upscale.

It is quite certain that at least a three-core cable will be used behind the box. You don't put a 16A circuit breaker on any crappy wiring.

With all due respect, that is nonsense. We also have a box here with RCDs, and about two meters further, there are the 50-year-old aluminum cables where the protective conductor and the neutral conductor are connected together(!) Really big laziness. But as long as the light was on, it didn't matter at the time of the renovation (mid-90s).

With all due respect, that's nonsense. We also have a box with RCDs here, and sometimes the 50-year-old aluminum cables are still connected about two meters further on, where the protective conductor and the neutral conductor run together(!) A huge case of laziness. But as long as the light was on, it didn’t matter back when the renovation took place (mid-90s).

Then your installation must be especially big nonsense ;-)

Absolutely agreed. I have seen things in junction boxes that can safely be defined as time bombs. I just wanted to point out again that an RCD before does not mean "quite certainly" three-wire behind it.

Then your installation must be particularly big nonsense ;-)

You have to look at the connected/installed cables!

If there are still stranded wires inside, then they are probably from the 1950s (or earlier).
Since around 1968 (IIRC), the protective conductor (plastic insulation) has been marked green-yellow.

From that time also come the DIN rails on which the components (FI, fuses, relays, switching devices) etc) still fit in their current design.

I just don't know whether I should now basically redo the entire electrical system "prophylactically" or just let it run as it is.

You can first of all relax - I wouldn't completely redo the electrical system, but I would check it thoroughly and modernize it here or there if necessary.