Read this about the Rooy Portable which is probably enough to answer all the technical questions I could possibly address and more include pictures, diagrams, and history.
My Rooy has the serial number 17500, which according to the link given above, puts its date of production in the first three years of production (I cannot tell if it is 1951 or 1952, but it does not matter to me).
Why do I write it is "Not Good Enough"? Because it is not "good enough". It is strictly designed around a very specific idea, to save space in all aspects while having a full sized keyboard and platen width. To this end, it is perfect. I do not think more space could be saved while retaining the features and typing action. However, exactly how important is this goal? Small portables such as the Skyriter and Baby from Smith-Corona and Hermes were made before this, and they were popular. Exactly how important to the typist was being even thinner and having such a pure design philosophy? I suspect, with good reason, it was not in itself very important. The issue with portables is that they need to be portable while still being usable.
The trade off of portability with usability is a balancing act. The closer the typing experience was to a standard, the better, yet the closer it was, the bigger it was. That is why typewriters did not get increasingly smaller. They still had to be used by the same hands to type on the same paper. Affordability was another issue. Making something was one thing, paying for it was another. The Rooy Portable looks expensive to make. Its size makes some parts more complex, and the ribbon is not standard width. I think it is 7/16" width. If people had the extra cash, they might have gotten this, just like I did, but as a serious typing tool, it works, but it is inferior to Skyriters and I suspect the Hermes line. That is what "Good Enough" means. It is a luxury item, something to show off. And that is what I am doing here. Showing off the expensive rare typewriter I found. I hope you enjoy it and are not too envious. If it is any consolation, having one is not nearly as fulfilling as hunting and finding it. It is here, and I can play with it any time I want, but when it comes to writing, it is last. The reason for this is mostly because of the French keyboard though, which like the French language, is just specifically designed to irk English speakers (I speak and read some French, but really, it is just really, really bad Latin).
Here are some pictures of my Rooy Portable, with a Skyriter popping in for comparison. Keep in mind that the Rooy is as it is presented. That is the fullness of the typewriter, whereas the Skyriter has its case separate.
The Rooy Portable!
That is about the size of it...
Here is a Skyriter for scale:
Here is the same Skyriter on top of its case to give a true representation of how compact the Rooy is (the top is a very important part of the typewriter, it is connected to the typewriter and necessary to be under it so the key levers can be pressed (trap door):
That is flat:
The Skyriter and Rooy in their cases and stacked on top of a Smith-Corona Silent's case (Silent is in side, but it is not like one can tell that). It is a different Skyriter because this one was closer...my Corona 3s were lined up in front of the two Skyriters and it was too far to reach to get the other Skyriter back out (I took this picture after uploading the others, realising I had not shown it folded up):
Now I am a true collector...an expensive typewriter which I do not plan on using (although it is important to me that it works) just so I can show it off. However, it is not like it is taking up any room.
On last thing, I used WD-40 to give life to the ribbon which was slightly visible at best. It worked, but this ribbon is slightly worn. I guess the original owner used it (got one's money's worth) and certainly if one paid that much (and wasn't a collector), one would use it.