Recently I saw this 120 Merz und Krell on Ebay and was curios enough to buy it. The seller guesses that it may be a prototype. Have a look at the pictures, that shows a normal 120 and the odd one to compare: I do not see any difference comparing the capsNo difference at the filling knob and nib endSame imprints and cap ring inscriptionsThe barrel color is darker on the odd one The big difference is the ink window. The odd one has a striped ink window, double the length of the normal one. It even shows with the cap on.It has fine longitudinal stripes in the barrel color on clear transparent plastic. I do not know how the barrel of the normal one is manufactured, but the ink window of the odd one shows clear seems on the nib and barrel side and seems to be glued in. Is there someone out there that could shed light on the origin of this pen?