The Standard Pen Co of Toledo Ohio made an interesting pen that utilized a proprietary sac to facilitate filling the pen. The pen is also seen under the Bolles brand, and in fact the patent was issued to W. Bolles, US patent 737697 September 1, 1903. The full patent and the patent diagram are shown below. The barrel is removed, and the sac has embedded bars on opposing sides, so the sac can be simply squeezed, but also be efficiently compressed the entire length of the sac.
Mine came to me faded, worn, capless and nibless. I recreated the sac by placing flat metal bars between two sacs as shown in the photos below.
It is interesting that the pen closely resembles the Boston or Colonial pen that uses a standard sac that is meant to be twisted, also patented in 1903. Both have removable barrels, and a short sleeve around the base of the sac attachment to the section.