After a near miss on one of these sets recently, good fortune came my way. It's the later two pan version with a bail retained 123R(and a pricker??). From the bail marks on the tank it looks like could be the original stove. It is missing the pot holder. I was surprised how much smaller in person it is than a Sigg Tourist set, I'd only seen pictures before. We fired it up before it came home to it's new caretakers location. I don't see any other makers marks on the pans other than the Optimus stamp on the lid. I do like how tight the lid fits. I'm planning on add a priming wick to it when I get some more material. I added the plastic thread protector idea from this forum . Thanks for looking.
It's are a nice compact unit. They can suffer from galvanic corrosion when the stove is left clipped in when stored away. Yours looks clean, congratulations.
@ROBBO55, I was reminded about galvanic corrosion with my new to me Sigg Tourist set. When I went to boil the inaugural pan of water in the set and found a small corrosion spot that was draining the pan(it was a receding boil. It took me awhile to see the leak. Where is this water coming from? Lol). I need to advance my novice tig welding skills before I attempt a repair.