Of course I will share this with you. Happy that I recieved so much information and knowledge here in the forum that will help a lot ...

You can listen to it live Wed 8pm CET, or download the podcast from the mentioned link later.  Will post again, though.

@ Ninive The circle with the prefix is the year of manufacture of the frame. You find that on the Unis models, and, as Uwe says, there is nothing lika that on the Germany-made models, so it seems you actually have a Yugoslavian machine. I suppose it was not by a choice by Unis to mark the frames, but a precondition by Olympia in order to be able to tell the one machines from the others.

Good morning, everybody! I am happy to announce that I have understood the tab and margin mechanism on my 1939 Olympia Plana A Enjoy!

Full review of this mechanism (photos to follow, for the time being see the images in the link I posted earlier in this thread; and many thanks to the guy who wrote that post sme years ago, as his observations helped me to go further and fully resolve the riddle):

There are two buttons right and left ot the space bar, both displaying two icons each. Both buttons may be rotated and will rest in one of two positions corresponding with one of the two icons. Both buttons have a small screw protruding from the stem, which results, depending on the position of the button, in one or two linkage systems being activated. Thus you get  four possible actions: (left button) Set margin, icon is horizontal line with two arrows rising from the two ends, Set tab, icon is one arrow rising from the middle of a horizontal line, and (right button) Jump to tab, icon is vertical arrow, and Clear tab and margin, icon is double horizontal line with arrow rising from the middle.

The mechanics at the back of the machine are the typical Olympia tab sytem: A series of little levers, one for each  increment all along the carriage. What the left-hand button does, is depress those little levers. For a tab, it will only use one link of the mechanism, and depress the respective lever in the back halfways. For a margin, the button, with the help of the little screw protruding, will activate both links to the back, thus enabling the little levers to be depressed further down. This is achieved by a thread, soft white material, the same that is often seen as drawchords. This thread pulls a  lever out of the way, so that the tab levers can go down further. The 5 center tab levers can only be used as tabs, not as margins. They are shaped differently, bigger, and therefore cannot go down all the way in oder to tr

*smile* I am officing around anyway, get email alerts for that topic and was lucky to have the Cella photo at hand on my website.

Cellas often sell at less than 10 Euros on Ebay, if you find one with local pick up in Berlin, I can handle that, pack it up properly and ship it. So, basically, you needn't really consider more than the shipping costs.

I think I have figured out what the reason might be for the erratic red typing of the Cellas. I have a "new" one with the same issue, another one coming in the next days, while the first one has been sold in the meantime as an all black machine. What I found:

There is a wire with a one inch loop that connects the colour switch with the mechanism that determines the ribbon lift height and links to the ribbon vibrator. The mechanism is located underneath the right spool. The angle of that wire, and the angle and position of its connecting hooks on either end, resulting in the wire not reaching its proper position in the mechanism and not being able to lift the ribbon vibrator to full extend every time aka reliable red. It is possible to push the wire manually in the proper position, and get a full red letter. Nice. Same when you manually lift the vibrator to full extend, nothing is blocked at that point. Therefore I don't think any other issues are involved.

I am considering hacking this by fixing a soft spring to the loop, in case I find a suitable spring and a good spot to fix its other end to, so that the wire gets a better angle. Hoping this will not affect the black position on the other side of the mechanism. Alternatively, I might unmount the ribbon mechanism to have better access to the wire, and rebend the ends. Hmpf.