Cross Century II Medalist - Loose part in barrel

[kevinoreilly9]

I should preface this by saying don't think this pen I've just received is a fake, but was surprised at it's light weight compared to my century rollerball given to me when was 18. There is a stamped number inside- 0612 (June '12?) 

 

In the barrel there is a part that is sliding back and forth. It is cone shaped and looks to fit snuggly in the end of the barrel, but it is loose but not able to come out of the barrel due to the threads. It looks to be metal. I've ordered a converter as it came with a small cartridge, so I'm wondering if when a cartridge is fitted it makes them fit snuggly.

 

Does anybody have any experience with this pen and can clarify why a part is moving back and forth freely in the barrel? Apologies for the terrible photos it is very difficult to photo graph inside the barrel