I confess that I would be no exception, were it not for a New Jersey pen friend's discovery of a Bender pen earlier this year. That got me digging into its story, and after managing to acquire the pen I was able to dig into the pen itself -- a story in itself.
Once all the added bits had been carefully removed, the original metal fitting became visible. Note that there is an axial hole running all the way through this assembly, including the external filling knob in hard rubber, which screws on the other end. The inner end of the plunger tube is mushroomed over, clearly to hold the piston washer. Below is the assembly with a new rubber washer installed, and with the hard rubber tube that covers the hollow brass plunger shaft.
As found, this tube had been pushed into the pen's body until it was flush with the end of the barrel. This must have been done when the pen was converted into a twist-filler, with the tube -- luckily, left uncut -- used as a bushing. Restored, it looks like this when extended:
Filling is done just as it is with a Chilton. The plunger is extended, a finger is placed on its end to block the central vent hole, the plunger is depressed, and the finger is then released, allowing the compressed air in the barrel to escape and the flattened sac to reinflate. The pen works exactly as described in Bender's US patent 825442, issued on July 10, 1906, noting that the patent does not specify the details of the piston seal.
772204 and 784538. Both dealt with internal valve arrangements of unnecessary complexity, likely never produced. His pneumatic-filler was a much better idea, however, and on October 19, 1908, The F. William Bender Company was incorporated to manufacture the new pen. As noted in Geyer's Stationer, vol. 46, October 29, 1908, p. 22:
ARTICLES of incorporation of the F. William Bender Company have been filed with the County Clerk of Hudson County, New Jersey. The company will manufacture fountain pens, with offices at No. 47 Newark street, Hoboken. The capital is placed at $50,000, divided into 500 shares of the par value of $100. The incorporators are Frederick William and Henry Bender, of Hoboken, and Conrad Goldbecker, of No. 183 Hackensack plank road, Weehawken. F. W. Bender, for many years in the insurance business at Hoboken, is the patentee of the pen, which is to be known as the “Bender Pneumatic Filler Fountain Pen." The pen is said to possess many advantages as a self filler. The holder is partly glass, though rubber covered, and contains a rubber sack. There is a plunger at the top, with an air vent which, when pulled out and released to settle back, sends out the air and draws up the ink. The company has a factory in Hoboken, but is looking for a New York location.A shorter mention in the American Stationer, vol. 64, November 7, 1908, p. 12, adds no details, but gives the name of the third partner as C. Goldbeck, rather than Goldbecker. As far as I can tell, no glass components can be found in our Bender pen.
How long did the Bender pen company last? It was still a going concern when the March 1910 edition of Polk's (Trow's) New York Copartnership and Corporation Directory was compiled (vol. 58, p. 77), but it is no longer listed in the 1914 edition. Bender himself died on February 7, 1912, at the age of 59. His obituary in the New York Sun of February 8, 1912, p. 7, col. 6, appears below:
From this account and others, it is apparent that for Bender the fountain pen business was a sideline. Only in the stationery trade press was his pen venture highlighted, as in this brief death notice in Geyer's Stationer, vol. 53, April 4, 1912, p. 5: "F. W. Bender, inventor of a safety fountain pen that has has considerable export business, died recently in his home in Hoboken, N. J." Where this export business might have been, remains to be discovered. As is, I have yet to find so much as a single advertisement for Bender's pen, or any mentions beyond what has been cited above.
Bender's last pen patent, 1098469, for an adjustable feed, was issued posthumously on June 2, 1914. The application had originally been filed on August 6, 1910, but was renewed on April 14, 1914 under the name of his widow, Pauline Bender, as executrix.