The Parker 51 is the world's most popular fountain pen. Over the course of it's 30-year reign, over 20 million units were sold all around the world. The development of this pen was completed in 1939, on the 51st anniversary of the Parker Pen Company (hence the name "51") and was released for sale in 1941. The 51 remained in production until the early 1970's, dominating the pen industry for over 30 years. 

The 51 came in several variants, but they can be classified into two main categories based on their filling systems. The Vacumatic and the Aerometric. This particular pen is the Aerometric variant. It utilizes a built-in squeeze style filling mechanism.

- Manufacturer/Model: Parker 51 Aerometric Mk II-B
- Year of Manufacture: Mid-1950's
- Color: Gold, Black
- Material: Plastic, Metal, Gold
- Nib: 14K Gold Fine Nib
- Filling System: Aerometric
- Condition Rank: B, Very good. Minor scratches and scuffs, filling system is working as intended.
- Country of Manufacture: United States

Condition Rank Guide:
-N: Item is in New Old Stock condition (NOS). Shows little to no signs of use apart from some minor handling wear.
-A: Item is in Excellent condition. Micro-scratches can be seen on the barrel, cap, and/or grip section. No noticeable scuffs, chips, or cracks.
-B: Item is in Very Good condition. Minor scratches and scuffs can be seen on the barrel, cap, and/or grip section. No chips or cracks.
-C: Item is in Good condition. Moderate scratches and scuffs can be seen on the barrel, cap, and/or grip section. No chips or cracks.
-D: Item is in Fair condition. Heavy scratches and scuffs can be seen on the barrel, cap, and/or grip section. May have small chips or cracks. See description.
-F: Item is in Poor condition. Item is not functional. For parts or repair only.