Parker's Duofold was the successor to its early pens, the numerous and various Jacknifes and Lucky Curves, appearing first in 1921 and lasting until the late 1930s. Its transition kept the Lucky Curve name, and its feed, for the first few years, but more importantly effected the shift from ebonite to celluloid, the Dupont brand it called Permanite. Duofolds came in Seniors, Juniors, Ladys, and Juniorettes, as well as desk pens, and are easily recognizable for their “derby” crowns and detailed imprints. Typical for their day, Duofolds are button-fillers, generally with firm to stiff nibs. They were very well-made, solid pens, so are often found today in surprisingly good condition, even after decades of steady use.