The Fisher Bullet Pen.

One of the best known pens of the 20th century - the Fisher Bullet pen. In 1948 Paul Fisher started producing the first pocket ball-point. The solid chrom-plated barrel body has a timeless design and is only 9.5 cm long when capped, but is nevertheless easy to use. From 1968 onwards, Fisher developed, especially for NASA space missions, a hermetically sealed, pressured cartridge which prevented the ink from drying up (with the slogan ‘still writes after 100 years'). These pens are used by astronauts.
The patented cartridge writes in space, under water, upside down, on greasy surfaces and in temperatures ranging from -34°C to +143°C. The pens are still tested by hand. The gas pressure (3.5 bar) ensures a constant flow of ink to the ball-point. With removable clip.