I just bought a Lamy 2000 with medium nib in an old book/stationary store that has a few vintage pens with very old prices and probably have been stored for decades. Got the lamy for 45€ because the old owner had no clue about today's value ... lucky me!
He also had a few Rotring fountain pens that I've never seen and can´t find any picture of them on the internet.
They are all black and looks like plastic, The cap has a diagonal cut and no clip and the bottom of the barrel is pointed and has a normal size (not long like a deskpen). Between the barrel and the section the pen narrows in a curve to give it a comfortable grip.
It's like the shape of a Parker Urban but the narrow part is closer to the section. The nib is a normal steel M nib and looked like a #6 or perhaps a bit bigger.
It takes standard international cartridges or converter (not sure if that fits because of the pointed barrel.
I didn´t dare to ask to take a picture ... because I thought I'd find it easily on the internet.
The old owner said they were also vintage pens like the Lamy 2000 and valued the pens around 25 euros ... which seems to me extremely cheap for a Rotring ...
Any idea of what Rotring model this pen could be?