This ia a very rare Montblanc 138 manufactured for the Italian market. 

The pen has a long ink window and it is in perfect working order. Unfortunately the engrvings on the turning knob are not present.

For a better understanding of this model, please visit the blog:

https://www.tenpen.it/article/montblanc-fabbricato-germania-why-and-where

Note: the writing sample says 136 but the pen is a 138.