This is Pelikan 100N from early 50s. It was produced until 1954. The nib is later. Was placed on Pelikan 400N and 400NN. Earlier than it was in 1956. The body of the cap or the clip is wrong. The cap must be of a knurled ring or the clip is smooth. It is easier to find a clip to be replaced. These pens are of poor quality material from the pens of the 30s and often celluloid appear tiny cracks. The pen should be cleaned to see what state is.
