HARO; The pen with a tip of glass
If you come across a pen with a glass tip, there’s a high probability that
'HARO' appears on it. HARO stands for HAns ROggenbuck who started
producing pens in Germany in 1926. Those were relatively cheap pens and
almost all that were produced had glass tips. The fountain pens had
different filling systems. There were safety fillers, lever fillers like
the pen from the 1920s in the picture above, and in the ad from 1944 a
vacuum filler is mentioned.
Glass tips have certain advantages that are listed in the ad to the side; there is a “mute” tip that makes it possible to write through several sheets of paper with carbon between. Everyone who writes with an ink pen holds it a little differently, so a tip wears according to the one who is using the pen. Glass tips on the other hand can be held however you like and the wear is a little more even. The final forming of the tips is such that one can draw a straight line with a ruler; they are also cheap and easily changed.