I have a question about Waterman No 5 celluloid pen Feed and the red nib.
I recently got this pen. The seller says it was cleaned and fixed with a new sac. It seems to be a new sac but not with a decent clean of the section and feed/nib.
So I tried to remove the feed but the nib came free and the feed is unremovable attached. There's a lot of caked old ink junk.
I guess I have to use a tapping tool and to do that I have to cut the new sac. Then I tried to pull the feed with a help of a rubber grip.
It did not work but strangely there's a small piece of black METAL BLADE ( used extra shape of the feed as to plug the section as friction tight ) came out. To my knowledge this seems to be a weird mechanism in a vintage pen and nib section??

So my question is there any vintage waterman pens have a section to fit the " nib/feed " have any metal PLUG ? or is this specific to this Waterman No5 with Red nib.
Other diagnosing is I find this nib is very wobbled even with this plug. You can easily pull out the nib alone free easily. Pen tends to blob easily if you shake.

I'd love to see any opinions or answers from you the experts on this pen or the watermen community. thank you again in advance for your time.