Parker originally produced 51 demonstrators for use solely by sales staff who were instructed that the pen must be used when selling a 51 and could not be sold.
Never missing a sales opportunity, around 1949 some Aerometric 'half demonstrators' featuring a clear Lucite hood were made available to the general public with a note offering an enhanced after sales service 'In appreciation, because your part in selling the new Parker 51 is so important we want your demonstrator to give peak performance, always'. This custom Cocoa model is one of these pens. It has the early chromed filler sleeve with the instruction to press the bar four times, the very first Aerometrics recommended six pushes. The clip is the long 'transitional' design, it was shortened in 1951 so 1950 is a good date for the pen.
The pen is in super condition, the barrel has a 'showroom' finish, the gold filled cap is ding free, and the hood has retained its clarity. The 'Parker, Made in U.S.A.' barrel imprint is still legible, as the imprint is situated just where the cap lip fits, it wears quite quickly with use.
The Parker 51 half demonstrator is a very rare pen and the Cocoa colour is one of the most sought after, this Custom version particularly so. The pen is, obviously, highly collectable.