This is not a pen, but a design object.
The inscription "Drehgriffel" appears on its hexagonal body. A derivation from Sütterlin, a source script for learning cursive script developed in Germany in the 1920s. This and a narrowly tapered tip, which, like the rotary knob, is contrasting in colour, distinguish the Drehgriffel.
The Drehgriffel Nr. 1 is a ballpoint pen made of precision milled aluminium and brass, lacquered and sealed. It contains a spring-loaded twist mechanism. To change the refill, simply unscrew the twist head.
The royal blue flow refill (thickness B), which has a particularly light and flowing writing characteristic, is available as a replacement refill in the colours royal blue and black.
Learn more about the iconic design object here.