Quite possible the seminal Parker fountain pen. First produced in 1941, introducing the concept of the hooded nib and with a production run in multiple countries which lasted for just over 30 years, this must be one of the best known modern day writing implements. Too young to have received a 51 before they stopped production, I came in to possession of mine after my paternal grand father died in the late 1970s/early 1980s (think I was 10-12 at the time).