From the nib was date coded

Dating parker 51 aerometric

They actually resemble the Parker Vacumatic clips in use at the time. They can be easily distinguished from later production by several unique characteristics. New Old Stock examples can be found with correct plastic filler, and some may have been switched as the result of a repair. As they wore, and due to the softness of the material, they became shiny and lost the machining lines. Another explanation may be that they were never dated or that the datecode wore off on most instances the datecode is lightly imprinted to begin with.

They actually resemble

Another identification aid can be the filler unit. Probably an experiment by Parker, most likely given to employees to test. Parker spent the same amount in dollars to promote the pen, but in reached million dollars in sales. As they wore, due to the softness of the material, they became shiny and lost most of the machining lines.

It's not uncommon for the First Year pens to differ in the colour shades from pens later produced. The first date codes, found for example on the Vacumatics, consists of two digits, the first one denoting the quarter of production, the second denoting the production year. On very early examples, the filler will not have the diamond struck at the end of the brass button. It is completely devoid of any markings. These pens had some distinct features.

Inside the cap the clutch is also longer. Most, but not all, had an aluminium filler with a diamond shaped imprint on the brass button, others came with the plastic filler. Some of these pens will incorporate early production materials, such as the caps and speedline filler.

It was the first pen that had the nib under a hood, the thought behind this was not to let the ink have a chance of drying on the way from the ink reservoir to the paper. The stamp initially had three dots and for each quarter one dot was filed down leaving none for the fourth quarter.

Right Oblique has the largest surface on right sided of point. The new gold nib that was to fit inside the hood was tubular and rather rigid. They dent easily and can get corroded and pitted.

They can be

There are however today reproduction jewels available in aluminium, so this feature alone is not a guarantee that the pen is a First Year. They jewels do dent easily and can get corroded and pitted. It seems as it Parker ran out of cap jewels first, and continued production with whatever was available.

Also the one-lined date code was situated at the end of the blind cap. In the second quarter of this system was however changed to save production time, and a new date code, using a system of dots, was adopted. These were however produced side by side with the standard line.

It should be noted that dating a pen by the nib can be very innacurate, as it is the most often replaced part on a pen. Note the distict features, Double aluminium jewels, metal filler with diamond imprint.

From the nib was date coded. The small digit denotes the year of making for the barrel.