It is amazing how different your camera is to mine, considering they are supposed to be the same model - or at least have the same name. As far as I know 'Ruby' refers to the shutter - which appears to be the same - and I thought 'Junior' was the size and 'Special' was the model? Maybe it is like the menu in Greek restaurants I went to once - everything was a 'special'
I've spotted two on ebbbeeeegeeebay, one which looks the same as your camera and one more like mine. I think these reflex cameras were produced for many years and I suppose there may well have been more than two versions, even with the 'Ruby' shutter? I'm pretty sure my model is the same as one in an advert I have from 1927.
I had to chuckle about the hidden screws. I suppose there's no point in hiding them if they always hide them in the same place!
Unlike your camera mine has no metal insert inside the wooden box (your camera seems to have a 'mirror chamber' - if that is a good name for it?). One advantage for me in this arrangement was that I could work on the shutter without fitting the mirror. I was able to slip it in and out of the mounting rails fairly easily with the camera assembled and so I actually left it out most of the time so as not to damage it.
I also had a new mirror made by Scientific coatings a few weeks ago... they only charged me £15 for mine, though