This is the only example of the Wirt double reservoir pen that I am aware of. It is huge. It is not imprinted, but clearly is the pen in the patent and the one intended by the ads. The ad shows a more rounded pen, which would have been more difficult to make on the lathe. I wonder if Wirt had a bit of P.T. Barnum in him, and advertised pens before they were produced and waited to see if there were orders. The patent describes using the large central portion of the case as a secondary reservoir. Down the middle is a more standard sized hard rubber tube that serves as the primary ink reservoir. The inner reservoir is open at the far end, but seals to the inside of the narrowed end of the barrel. When the section end is unscrewed, the narrower inner reservoir opens up to the outer secondary reservoir so it can be refilled.
My crude drawing to show how I believe it was intended to work. Refer to Fig. 2 in the patent drawing.
- The barrel is filled. The inner reservoir is open at the far end to let in ink.
- When the section and inner reservoir is inserted, ink fills the inner reservoir, and the end of the inner reservoir seals into the end of the pen.
- When you run out of ink, you unscrew the section, disengage the seal at the bottom, and the inner reservoir will partially fill from the bottom.
- Based on the shape of the bottom end, you can repeat this process and eventually get every last drop of ink from the outer reservoir to the inner.