This is a Parker 51 Aerometric finished in Black with a Rolled Gold cap. Made in the USA, this is a very good example of this model which dates from around 1955.
The pen is fitted with the reliable aerometric filling mechanism which has been fully serviced. It is fitted with a lovely smooth extra fine nib and is in overall excellent condition with only very light wear marks and scratches commensurate with light use. The cap has the uncommon continuous parallel line pattern (rather than the more common groups of lines) and is in very good condition with one minor ding.