Do-Write Piston Filler

[Gutbucketeer]

I have been cleaning up a Do-Write Piston filler that I won on Ebay. See the pictures. I have been able with soaking, and ultrasonic cleaning to get the nib and feed out, and get it pretty much cleaned of old ink. However, the old simple piston is now detached from the plunger seal and can come all the way out. So here is my question. How can I open the pen up to replace the plunger sealer? Were these old piston fillers glued at both ends, or does one end screw into the barrel? If they were glued in were they typically glued using glue I can heat and loosen or not?

You can see at the end of the pen a ring around it where the barrel and screw part for the endcap meet.

 

Or will I have to saw the pen in two and then add an insert to reseal it?

 

It will be fun to try to get the pen working again, but It may end up being just for parts.

JAB