1939  Development completed on the 51st anniversary of the Parker Pen Company.

1939-40  Parker "51" test-marketed in South America and Caribbean countries.

1940  Parker "51" test-marketed in selected U.S. cities.

1941  The Parker "51" is introduced in the U.S. market.

1941  Parker "51" Ink introduced

1946  Parker "51" Red Band filler introduced and made for approx. 1 year

1947  Parker "51" vac demi introduced and made for 2 years

1947  Plain arrow clip introduced

1947  Blue Diamond clip discontinued mid-year 

1948  Last year for vacumatic "51"

1948  Last year for vacumatic demi Parker "51"

1948  Aerometric Filler Parker "51" in demi and full sizes

1948  Parker "51" Signet in all gold filled cap and barrel

1948  Superchrome Ink introduced

1949  Parker "51" Presidential in all 14kt cap, barrel and clip

1949  Parker "51" Flighter in all stainless cap and barrel with gold cap band

1950  Parker "51 Special introduced

1951  Arrow clip shortened

1952  Last year for barrel dating on pens

1954  Parker "51" Jotter ballpoint introduced

1955  Liquid Lead pencil introduced

1956  Last year for pencil dating

1957  Rotary pencil introduced for regular "51s"

1957  Last year for Superchrome on filler sleeve

1958  "Signet" model renamed the "Insignia"

1958  "Bandless" Flighter introduced and made through 1960

1958  Parker "halo" logo added to cap

1960  Breather hole moved to the side of barrel

1961  Demi model discontinued

1961  Converter version introduced; made only approx. 2 years

1962  Finger clutch introduced

1964  Cap "lip" removed

1965  "51" imprint on cap

1965  new one-piece filler sleeve without black plastic end cap

1969  MKII introduced; "61" look-alike with pearl jewel cap, greater barrel taper, flat end

1971  MKIII introduced; same as MKII but with chrome jewel

* Years are as close as possible, but it must be noted that most changes often took place over a period of months.  It is also very common to find pens that have been fixed over the years and have parts exchanged with earlier or later models