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 first 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. Later, starting in 1930, Duofolds adopted tapered barrels and caps, and were now Streamlined Duofolds; their lengths at each model were a few millimeters shorter s well. In the late 1930s, these later Duofolds transitioned into the vertically striped Striped Duofolds, which appeared in two generations, the button-filled models and then, until 1948, as Vacumatic-filled models (now often called Duovacs). There has always been some confusion among the overlapping models of the 1940s, but to me, if it carries a Duofold imprint it’s a Duofold; that plus a Vacumatic-filler makes it a Duovac, the Vacumatic-imprinted vertically striped pens are Vacufolds; but even the experts admit that there are more variants than can be named. Typical for their day, Duofolds generally carry 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.