I purchased this pen without knowing enough about it.
After some digging around (and with some help from the friendly people at fountainpennetwork.com) it turns out that this is at least two different pens.
The barrel is a Montblanc 146 piston filler. This is easy to tell because the imprint on the piston knob reads “146”. However, if it were a 146 from the 1950’s, then this would mean that I would expect a two-tone “4810” nib. This pen has a #6 single-tone gold nib – which was normal for a Danish 246.
The cap is from a Danish 246 piston filler. It has the double-banded cap and a small-diameter finial (the screw that holds the clip onto the cap).
So, it seems that this is two pens – a German-made 146 barrel and a Danish 246 cap and nib.
So, it’s not a “pure bred” pen – but it is certainly lovely to write with (although the nib sings a little if you’re moving quickly).
The clip has some signs of brassing – probably from previous polishers, but the remainder of the metal on the pen is in good shape. The barrel and cap have minor scratches.
Update: I’ve decided to use this pen as a source of repair parts for other pens in the future. The first portion to go was the nib, to fix a Danish Montblanc 206.