Val..where are you?

The arm is actually a Hornady based on web photos.  Not a home made measure though.  It is cast so it was probably a prostitution run.  I will make an adapter for B&M tubes and see how accurate it is.  The steel shaft runs the full length.  If I like it I will have to modify it.  Not sure what it mounted to.

I can't help with the measure identification jack, but I could enable the addiction easily.  I'm on a long term slimming down/cleanup plan.  I have a box that I throw unknown stuff into; it fills shockingly fast as what I don't know is extremely vast.  Since you like this game so well, I could ship you a flat rate box every time it fills for a nominal price! 

I've resorted to throwing stuff into the scrap metal and garbage that I can't figure out.  Last sorting session, I threw a bunch of unknown sears and tumblers and a known but rust pitted ballard double set sear into the garbage just so I didn't have to deal with them.  I sorted through a few pounds of gun screws; put the ones I could identify into my multiple divided tackle box system and walked over to the scrap metal and dumped in the remaining odd ones that I'm not going to give a home to anymore.  Tossed a real nice holster that someone had cut to start modifying.  I don't have the space or patience to store any of that stuff anymore, and don't have the desire to find it an appropriate new home.  I do sell occasional lots on ebay; the last one of beat up and mis-matched colt grips brought more than $100.

The more I think about this measure the more I believe it is intended to throw shot not powder.  The center pivoting chamber can take inserts to control volume.

Here is a top view showing where inserts could go.