I thought I'd posted this before, but I'm not seeing it:
Marked "Patents Pending - Brown & Bigelow - St. Paul, Minn USA"
Move up to this week and what did I find?
The previously-found refill is on the left, and the other came out of this Redipen. The left-hand Acme thread at the end engages a nut inside the cap of the pen to advance and retract the refill. A very solid design in a very solid (enamel over aluminum) pen. The "older" refill is just slightly shorter than the "newer" one, and may be adapted to hold a modern ballpoint refill one of these days.
And since the older refill was simply pressed together, and not very solidly at that, the threaded end bit (with a wrap of Scotch tape to enlarge its OD) now carries a Uni-Ball 207 gel refill (shortened by 1/8") that fits beautifully into the tip of the pen.
The core inside the outer tube is a (badly) machined Archimedes screw that was presumably meant to be turned to carry ink to the tip. There's even a coil-spring clutch mechanism to only let it turn in one direction! Nine parts in all, including the ball.
-- Edited by Chthulhu on Sunday 8th of February 2015 10:25:51 AM