This is a Parker 51 Vacumatic finished in Black with a Sterling Silver cap. It was made in the USA and dates from around 1947. The Vacumatic 51's are a lot less common than the later aerometric models and use the pump system borrowed from the earlier Vacumatic range.
The cap is made from Sterling Silver and has a gold filled clip with the famous Blue Diamond, Parkers symbol for their lifetime guarantee. The pen has been fully serviced and a new diaphragm has been fitted. It is fitted with a lovely Medium nib and is in overall excellent condition with light wear marks and scratches commensurate with light use. There are no dings in the cap, only light marks.