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In fact, although functional and efficient, the [[Crescent Filler]] had its worst flaw in being unpleasant from an aesthetic point of view, and despite a strong promotional campaign that emphasized its merits (Mark Twain, taken as testimonial, endorsed the advantage of it not allowing the pen to roll down from the table) with the appearance of [[lever filler]] pens the sales began to decline increasingly, despite that the new mechanism was inferior from a purely technical point of view.
This is why in 1921 also [[Conklin]] started producing models with a peculiar [[lever filler]] mechanism, ingeniously constructed so that only half of the lever was in the open. With the introduction of the large dimension pens trend started by the [[Duofold]] also [[Conklin]] introduced in 1923 the [[Duragraph]] model. The following year the [[Duragraph]] was renamed as [[Endura]] and the production was converted to celluloid. Initial model were in black or red hard rubber, but soon they were produced in celluloid, with different colors like ''Rosewood'', ''Black & Gold'', ''Lime Green'', ''Lapis blue'' and the rare ''Blue & Gold''.
[[Image:Conklin-Endura-Colors-Set.jpg|thumb|A set of [[Endura]]]]
The last [[Conklin]] important model was the [[Nozac]], designed by ''Louis Vavrik'' and introduced in 1931. [[Nozac]] is the only American pen equipped with a [[piston filler]]; it had a transparent tank with large ink capacity (further highlighted, since 1934, by the ''word gauge'', a scale that measured the number of words remaining). The pen, produced in beautiful color and with a multifaceted body, is one of the best model of that time, but the mechanism, derived from that one of a mechanical pencil, was not particularly robust and efficient and the pen did not have the success that it would have deserved. In 1937 a [[plunger filler]] version of [[Nozac]], called [[One Stroke]], was produced.
The company was still declining and in 1938 all the [[Conklin]] assets were transferred to the investor group ''Chicago Interests''. The following year Toledo plants were closed and the production was moved to Chicago. The previous models remained in production during the war but few pens were produced. In the following years the production continued to move towards the low end of the market with economic fountain pens to and a low cost ballpoint. Although some of these models, like the [[Glider]], have some collectors interest, the [[Conklin]] production progressively reduced in quality and quantity, to completely cease in 1948 (or 1955?).