Parker 51 Classic in Teal. Superb Broad Nib. 1968.The Parker 51 with the aerometric filling system was introduced in 1948. About twenty years later the Mk. 3 pen, with a squared off barrel and a more tapered cap was introduced. This is an intermediate pen with the original rounded barrel but the final version filler sleeve and the new style cap, it was not unusual for Parker to 'overlap' models in this way during transition. The colour, named after the wing flash of the teal duck, is most attractive,