The Parker 51 is perhaps one of the best known of fountain pens, a groundbreaking design, and and one that proved profitable for Parker for almost forty years. Produced in several countries, and in a number of versions, the 51 is a popular pen among both new and experienced collectors. The reasons for it's popularity today are not very far removed form the reasons it was so popular when first introduced; the 51 is a great writing pen, and it comes in a large enough array of colors and cap styles to keep a collector dashing around after new additions.

The 51 was launched in 1941, but it initially came out of research and development in 1939, the 51st year of the Parker Pen company. The name was considered to be a good idea from a marketing standpoint, being short, simple, and easy to translate into other languages. The pens made during the first year of production are slightly different form later pens, which makes them considerable more valuable to collectors today.

The Parker 51 continued, with some changes, through to the 1960s in the US, and in the UK and South America, production carried on until as late as the early 1980s. Not bad for a pen first conceived in the late 1930s!

In the Vacumatic filler 51s, there are two principle designs found. Most will be the later plastic filler version, these are found on the pens made from 1942 through the end of production of the Vacumatic fill 51. The First Year 51 pens, those made during 1941, will usually be found with the aluminum Speedline style filler. The Red Band 51s were made only for a short period of time, these are a sort of button filler version of the 51, and can be identified easily by the bright red threads for the blind cap, and the steel filler mechanism.

First Year 51 pens are identifiable in several ways. Perhaps easiest is the fact that, unlike later models, the date markings are not at the top of the barrel, near the clutch ring, but are located along the lower edge of the blind cap. The cap and barrel jewel are usually made of aluminum, instead of the pearl plastic used on the later production. If you remove the blind cap, the filler gives a clear indication of the First Year pen, instead of the plastic plunger, the First Year 51 use an aluminum filler identical in appearance to the Speedline Filler used on the Vacumatic pens of 1937-1939.

The 51s made from 1942 through 1948 constitute the bulk of the vac filler versions found today, and range form fairly common and affordable versions to very expensive showpieces. Color is probably the primary factor in determining value on these pens, since the caps are easily interchangeable. In order of rarity the colors found are: Mustard, Nassau Green, Buckskin, Cordovan Brown, Cedar Blue, Gray, and Black. In addition, these later production models were available with either the double jewel barrels, or with the single jewel version. Double jewel 51s command a premium over the single jewel pens in most cases, however, a few colors are actually more common in double jewel form, Mustard, Buckskin, and Nassau Green, for example, are much harder to find in single jewel form.

In 1946, the new non blue diamond arrow clip was introduced, by the end of the year it was used on all the 51 pens. In 1947 Parker launched a smaller version of the 51, called the Demi. This was available in the same colors as regular production 51s of the time. The Vac filler was discontinued in 1948, with the introduction of the new Aerometric fill mechanism.

In 1948, Parker announced the launch of a new 51, with a redesigned filler mechanism, called the Photo-Fill. This system used a simple pressure bar fitted over the sac, when the barrel was unscrewed from the shell, the bar could be pressed with the fingers to fill the pen. The new ink sacs were made of a clear material called Pli-Glass, which allowed the ink level to be seen. Within a couple of years, the Photo-Fill was renamed the Aerometric. The new colors available in these pens were: Black, Dark Blue, Teal Blue, Dark Green, Gray, Cocoa, Burgundy, and for a short while, Plum. In addition, versions were available in stainless steel cap and barrel as the Flighter, in gold fill cap and barrel as the Signet, and in solid gold as the Presidential.

The Parker 51 has proven to be a very popular pen with both collectors and users, and perhaps as a result, it has been one of the more commonly customized pens. The range of new caps available for the 51 is enormous, and customizing a 51 can be as simple as slipping one of these modern caps onto your favorite 51. Other choices range form new barrels in different materials, to complete handmade pens, even rollerball or ballpoint conversions.