The Parker Pen Co. was founded in 1888 and produced its first pen in 1889. By 1894, they had devised a curved handle on the top of their pen which stopped leakage, a selling point for early Parker Pens. A long-standing symbol of a fine writing instrument, Parker Pens have become a collectors item. True collectors like to verify and authenticate their Parker Pens. There are a few distinguishing characteristics that the company has used over the years on its products.
Locate the Parker Pen clip. The shape of the pen clip is often the company symbol of an arrow complete with vanes or fletching. The tip of the arrow is pointed downward with the vanes near the top of the pen cap.
Look for the name "Parker" on the pen. It might be located on the cap, clip, or pen band.
Open the pen to reveal the ink cartridge. Parker makes ink cartridges specifically for their pens. The ink cartridge will bear the Parker company name.
Look for the "H" located on the gold of a Parker Pen. The George W. Heath Company did the gold work on early Parker Pens. They stamped an "H" signifying their company symbol on Parker Pens.
Reference your pen against the Parker Pen catalogue. Their are collector sites such as Parker Collector which detail the older pens in the Parker line. Search through the catalogue to determine if your pen is an authentic match to one of the many pens they have produced over the years.