Montblanc 254 - Medium Stub nib (SB556)
Nib: 14 Kt Medium Stub
This is a Montblanc 254 from the 1950s. The turning knob looks like a replacement to me, and it has a tiny crack in it that seems to have no functional significance. It's a fun pen with which to write, a nice size, and other than the turning knob, in great condition. The nib isn't marked, but appears to write as a medium stub. 5 1/4", 133 mm.