I do not have a Spaceview but the regular model. Marking is M6 making it 1966 vintage. It wakes me up at night if I leave it on the wooden dresser in the room. If it is sideways at the right location the whole resonates like a guitar and you hear it across the room.
When I got it a while back it had been damaged due to a leaky battery and it had been stored like that for a decade.
Took me a long time to fix and get running properly but I don't remember it being particularly tricky to open. I did have Omega's dismantling and repair instructions on CD from a while ago to do the repair.
I re-phased it (under binocular microscope) to use a regular 1.5V button batteries since the original mercury batteries are hard to get. Note that some watches cannot be made to run properly that way as you will end up at the end of adjustment or with double stepping on the index wheel. In that case, your other option is a voltage dropping diode. That would be easy to do nowadays with the availability of ridiculously small SMD diodes! I also machined (not visible from the outside) the inside battery hatch button to accommodate the cheap earring aids batteries of the time that were thicker than the original.
To check its accuracy a simple phone pickup coil (black blob in photo) coupled to an Ithaco low noise preamp is fed to a frequency counter. No need of a microphone.
I still wear it occasionally. A nice piece of history.