It is presumably the Montblanc 215, which was produced between 1957 and 1959. The model number is usually stamped on the barrel band and should be checked for confirmation. As a refill, a Ballograf refill is also suitable. For value determination, reference is made to Axel's forum article on the value determination of Montblanc writing instruments; as a market price around 30 euros is mentioned, comparable to the Pix 276.