Richard

This is a modified Post (pull, or syringe) filler. The plunger is partially collapsible to allow a larger reservoir with a shorter blind cap.

Rick is right about the feed. I don't know any companies other than Sager that made feeds like that. This one looks pretty early; I can't see any comb serrations. The blind cap and the threaded boss recessed into the back of the barrel also sort of suggest that Sager might have had something to do with this pen, given Sager's plunger filler design, and the fact that the owner could just put ink into the barrel and use the pen suggests that the barrel is sealed to the section, another point in favor of a pen like Sager's, with the barrel used as a reservoir.

There was a Hamilton Pen Company in Chicago in the 1950s. Since St. Charles is a western suburb of Chicago, I'd guess that we're talking about the same company — but I have no further information on it and so don't know when the company was founded. It appears not to have held any patents, so that avenue of research is closed. It's not impossible that Hamilton was merely jobbing pens from Sager (or, not as likely, some other maker). Since Sager was also located in Chicago, this looks to me like the setup for a fairly neat package.

Marc, this is all speculation, so if you or any of your IM team are caught or killed, the Secretary will disavow any knowledge of your actions. This tape will self-destruct in five seconds. Good luck, Marc.

Bubbles at the point where the feed enters the section are normal; if there were none, I'd be worried.

I don't know of any sort of seal near the feed. The following image shows what should be inside the pen. (This isn't a Craftsman; the Craftsman has no separate metal thread ring.)

The Touchdown tube is secured to the blind cap with a self-tapping screw that encloses a seal. What is the "connector" you mention?

I've had good results with Scotch Magic tape. A full wrap clockwise as you look at the section from the sac end, and screw it in. If it's still too loose, take the tape off and try two full wraps. (Never use half a wrap, this can create uneven stresses.) The worst case I've ever encountered was a Skyline that took three wraps.

I picked up one of these a few months ago and there is quite a bit more engineering to them than I expected.  I never found the ball bearings that I understood were part of the section end.  Either they weren't there in the first place or they were lost by someone else.

 

Is white the actual color of that cartridge?  Mine was translucent, much like todays carts.

The ball bearings were eliminated after a couple of years. When they were there, they were in notches in the section where the pimples on the clutch ring are located; thus, they fitted into the insides of the pimples (the dimpled side) to provide backing strength, with the effect of making the cap closure more solid.

The cart is translucent; I shoot against a white background.