Ok, I just got to disassemble it to check things over to see how things look inside a pen that is almost a century old. The section is friction fit to the body so I just pulled it out, the sac was new as it was installed by the vendor. I put everything in my ultrasonic cleaner and let it run for 3 sessions of 6 minutes each, then reinstalled everything. The sac is 50mm long (2 inches). I will order some new sacs for back up. Everybody said to use SHELLAC to 'glue' the sac back onto the section but I did not have any so I just used the clear silicon sealant. It needs 24 hours to set.