Montblanc StarWalker platinum fineliner pen in black resin with platinum trim. The top cap is transparent with the Montblanc logo on the blue dome, representing earth as seen from space. The StarWalker Doué comes with a platinum-coated cap and fittings and a black precious resin barrel.
This pen uses Montblanc fineliner or rollerball refills.
If you prefer to post your pens, it helps to know that this cap screws in place in one turn.