Hi and thanks for your responses !
Cheeky > Yep, this flektogon isn't a great performer, just an average lens, not too bad but not phenomenal either. Is sharpness is below-average, in my opinion, and it's not MC (so, lot of flares). But the colors/bokeh are amazing if you're lucky enough to shot with the good conditions/lights. Also, this lens produces great images in low light, which is not necessarily true for others lenses of this kind.
It's certain that if I sell it, it will be as a collector item.
About Ebay, I never thought about this possibility, I think it's a great idea to let the market evaluate the price, thanks ! I don't have any illusions about the amount of money I can get with it, but you're right, we never know
Jatrax > If I remember well, the "Star Wars" thing is just a nickname, not an official version of the product. The Karl Zeiss fandom named this kind of lenses relative to the movie because of their aspect (lot of black/orange/silver colors).