This button-filler pen appears to be a Danish Montblanc Simplo No. 2 with the bandless, tapered “flat top” cap. The production run for that model of pen was from 1937 to 1946.
The clip on this pen is somewhat different from the pen shown in Holten and Lund’s book “Montblanc in Denmark 1914 – 1992 – The Untold Story“, and is more like the clip on the “Montblanc De Luxe” 132, which was imported to Denmark from Germany from 1935 to the 1950’s. The same clip also shows up on one of the Danish-made Montblanc mechanical pencils from the same time period. I don’t know if this means that they just took another clip off the shelf when this pen was produced, or if it was repaired once-upon-a-time.
Although the No. 2 nib is in excellent condition, this pen has been somewhat neglected in its lifetime. It appeared as though a corrosive ink was allowed to sit in the pen for a long time, which leaked and ate away at both the pressure bar and button. Neither survived. So, the pressure bar has been replaced with a new one, and the button has been replaced with a vintage brass button from another Danish pen made by Niels Benzon’s Benzon Trading Company (who occasionally had cross-production agreements with Alfred Th. Øberg A/S – the Danish Montblanc factory).
The imprint on the cap is in great shape, however, the imprint on the barrel is somewhat worn in the middle, as can be seen in the photo below.
Total weight: 15 g
Body weight: 9 g
Total length (not posted): 112.3 mm
Total length(with cap): 127.3 mm
Barrel max diameter: 10.7 mm
Cap max diameter: 12.3 mm