For sale is a vintage Montblanc 31 fountain pen.

• The Model System: In the 1960s, Montblanc used a two-digit numbering system. The 31 is the steel-nibbed version in its tier. 

• The Nib: It is made of stainless steel. I estimate it to be medium width (it is not marked)

• Filling Mechanism: This is a piston-filler pen. You unscrew the blind cap at the very end of the barrel to operate the internal piston and draw ink from a bottle. The piston operates correctly but is quite stiff to turn.

• Ink Window: There is an ink viewing window on the pen section. On this 31, this window is  blue. 

• Cap Details: The cap unscrews to reveal the section. The top of the cap features the iconic snow-capped mountain (or white star) Montblanc emblem. The is also the emblem on the base of the barrel.

• Size: When capped, the pen is about 128 mm long, with a barrel diameter of roughly 11.5 mm at its thickest point. 

This pen is 40 years old and has been used, but is in reasonable condition. There are no cracks, but there are microscratches.