Parker's continual advertising during the war created demand that took several years to fulfil after the end of the conflict.

The initial model used a Vacumatic filling system which operated by pressing a plunger to generate a vacuum, drawing ink into the pen.

[2] In addition, Parker reformulated its "51" ink, reducing the alkalinity, and introducing a selection of bright colors, and changing its name to Superchrome.

This initial ink was highly alkaline and while water-based, also included a substantial amount of isopropyl alcohol.

The formulation in the ink would react with other manufacturing materials (such as celluloid) of the period leading to irreparable damage to other fountain pens.

A pilot who is suspected of falsifying flight records in their logbook in order to overstate their actual experience is said to have logged "P-51 hours".

[5] The 51 is popular with pen collectors, and in 2002 Parker issued a lookalike model called the 51 Special Edition.