This was my first exposure to this type of pen. Of course, when you look at a parker vacumatic this makes perfect sense in terms of filling mechanism - use the elasticity of the sac to make the vacuum.
I like the overall simplicity of this pen and the size is very nice as well.
It was a bit of a bear to get apart. I had to soak, heat, and repeat often.
I used a single website to help with this one:

https://www.pm-pens.com/category/bran...

I had to do some problem solving with this one. It wasn't clear to me just how long/short the sac should be cut and whether the plunger was the correct length after it had seemingly crumbled/deteriorated a bit. In the end I think I made reasonable decisions.

I hope to stumble upon some more of these pens eventually and to broaden out my collection to other European brands. I already have some that are nice piston fillers that I'll have to learn about and share. More to come.

If you know anything about these pens or have examples of your own, please share and comment!