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I have a mysterious nib and feed. Before I knew anything about fountain pens, I disassembled it and threw out the body because it was inky and I hadn't realized that I needed it. I would like to find a replacement body. The nib doesn't have any writing or anything on it. It fits cartridges from my Pilot Parallel, hence my suspicions that it is a Pilot pen. I don't know how old the pen is. 

It writes pretty dry, but it writes. It also seems to be able to flex a little bit, as shown in the pictures.