Piston filler with detachable rod

This Reform fountain pen has a fairly standard piston. However, the ink capacity is much better since the entire barrel can be filled. This is accomplished by having a removable rod that attaches to the piston via a hole in the end of the barrel, and can be unscrewed and detached when the pen is full and in use. I have seen this referred to as a “wand filler.” The flaw with this approach is that one must keep track of the rod when not in use, as it cannot be left attached to the pen when it is full of ink. (Photos courtesy of Barry Eckhouse.)