The history of the pen is as follows, note that there is inconsistency amongst the experts about the names of the different types of 51, some regard the Vacumatic 51 as a seperate entity and the aerometric is the Mk I, I prefer to follow David Shepherds philosophy as outlined below; Above: The mid 1970s saw the final version of the 51 Aerometric - the Mk3. This had the later 61 cap with metal clip jewel. One important change was that Parker changed the type of plastic used for the shell and barrel to a softer version which is prone to shrinkage and also distortion from the pressure of the metal clutch inside the cap. Threading on the front shell and barrel was also coarser than on the Mk1/Mk2, so parts from these models will not fit the Mk3 So what made the original '51' so significant? The whole ink feed system was special and new. The hooded nib only just emerged from the pen's grip section right at the tip, which meant ink could be wrapped around it. The nib itself was actually a little tubular shape, with the ink feed running through the middle, and a 'collector' wrapped around the outside. If you've ever looked at a modern rollerball with a transparent grip, and seen those fins inside, with ink between them, that's what the collector is like - like the Pilot V-System range. A series of closely-spaced fins that can gather ink, holding it wrapped around the nib. This keeps the nib wet, with a ready supply of ink.

Queen Elizabeth used a burgundy Parker 51 since the 1950s. [12] Parker as a company has received a Royal warrant of appointment as the official providers of writing instruments for the Royal Family. [13] Appearances in media [ edit ] The 51 was a unique product and shook the world on its introduction. The torpedo shaped design and the hooded nib became icons of style and were copied by virtually every other pen manufacturer. It is no exaggeration to say that the Parker 51 is the most popular, reliable and functional pen ever invented.From conception to assembly, the attention to detail is second to none. The cap is decorated with a complementary metallic jewel and each finish is inspired by heritage colours of the past, a tribute to the original Parker 51 range. Inspired by the past. Made for the future. Above lower: In addition to the full size 51, Parker also produced a demi aerometric version. This was identical to the larger pen, just proportionally smaller in all respects including the cap, and was in production until around 1960

The Vacumatic filling system was developed by Parker in the early 1930s. Ink is drawn in to the pen by repeated pushing of a plunger at the end of the barrel. This flexes a rubber diaphragm attached to the plunger with the partial vacuum drawing ink into the barrel. Ink is held directly in the barrel - the pen does not have a conventional ink sac Above: A 51 Aerometric Mk1 from the mid 1950s showing the shorter clip. Most 51s found in the UK are similar to this, with production running until probably at least the late 1960sIn 2021 a reimagined version of Parker "51" was released. [9] [10] The 2021 model had slight differents with its predecessor, being 4mm longer than the original 51. [11] Parker's continual advertising during the war created demand that took several years to fulfil after the end of the conflict. In 1947, Parker’s factory in England also started producing 51s for the British and European markets and, with the Vacumatic filling system being seen as overly complicated, Parker worked towards a new type of filler which was longer lasting, more reliable and simpler to use. In 1949, the ‘New Aero-metric Parker 51’ was launched in the USA and described as ‘a clear case of improving on perfection’. Instead of the button operated rubber diaphragm filler, this new 51 came with a PVC pli-glass reservoir with a 30 year life expectancy - an astonishingly long life given that most pens then required a service every 5 years or so. In the event, even this projection proved to be a little pessimistic as 51s continue arriving here every month for their first service and sac replacement in 70 years! English production of the Aerometric commenced at Newhaven in 1950. This aerometric filling system was used in virtually all 51s until 1978 when production in the UK ceased. Small changes and improvements to the 51 continued almost annually from 1950 on with the major redesigns in the late 1960s with a streamlined Mark 2 followed by the final Mark 3 version in around 1975. A wide range of 51 variations were produced in both the UK and USA with slightly different timelines, and it is not unusual to find different colours, cap styles and imprints in US and UK production

Lauren Hubbard. "Queen Elizabeth Has Used the Same Brand of Pens for Almost 60 Years". Town & Country Magazine . Retrieved 10 Jul 2021. wanted’ – retaining its distinctive streamlined silhouette and iconic hooded nib; yet is made for the future – this pen is hand assembled and made from durable precious resin, benefitting from Parker’s expertise and reputation for superior craftmanship.Above: A 51 Aerometric Mk1 from around 1950 showing the long clip which was in use from 1948 to around 1951 The filling system was re-designed in 1948, with the introduction of the Aerometric filling system. This filling system operated by pressing a pressure bar on "Pli-Glass" PVC sac. [2] For deliveries to the Rest of the World, Royal Mail suggests up to 21 working days for parcels to arrive. The pen was not named after the P-51 Mustang fighter plane; but Parker took advantage of the coincidence by comparing the pen and the aircraft in its advertising. Above: In 1947-48 Parker produced a demi-sized version of the 51 Vacumatic. All parts except for the barrel and cap were identical to the full sized 51. An uncapped Demi is about 11.2cms long whereas the full sized 51 is 12.8cms The Parker 51 Aerometric

While the same design of collector isn't often used in modern pens, it's very normal now for pens to have a lot of fins connected to the feed, holding ink close to the tip and ready for use, even in rollerball pens. The collector lives on, influencing the design of many pens all over the world. The pen and the ink were both named "51" to mark 1939, the company's 51st anniversary, during which development for the pen was completed (U.S. design patent No. 116,097, U.S. Patent 2,223,541 filed). By giving the pen a number instead of a name, Parker avoided the problem of translating a name into other languages. First Year 51 Vacumatics produced in 1941 differed in some respects from the 1942-48 production. The most obvious variations were that the barrel imprints were at the filler end rather than next to the clutch ring, and both jewels were metal rather than plasticThe Parker 51 is a fountain pen first introduced in 1941. Parker marketed it as “The World’s Most Wanted Pen,” a slogan alluding to restrictions on production of consumer goods for civilian markets in the United States during World War II. The"51"was innovative for the period. It had a number of new design features—in particular the hooded, tubular nib and multi-finned collector were designed to work in conjunction with the pen's proprietary, fast-drying "51" ink. This allowed the tubular nib to stay wet and lay down an even line with either "51" ink or conventional inks. The initial model used a Vacumatic filling system which operated by pressing a plunger to generate a vacuum, drawing ink into the pen. [1] Shepherd, David; Shepherd, Mark (January 2004). Parker "51" (1sted.). United Kingdom: Surrenden Pens Ltd. pp.102–104. ISBN 0-9546875-1-5. TheParker "51"stayed in production until 1972 with a series of revisions throughout its production cycle.