Silver are you sure that's a Junior Gent?
I have some of those kits given to me from a friend they have the rubber o0rings in them and the same finial on the cap which differs from the Jnr Gent.
I could be wrong but when I sized up the bushes they are a different size and yours looks a bit on the lean side at the flanges.
There should be o0ring on the top of the pen for posting cap to.
Sorry to criticize but I want to be sure for when I make my kits up.
This is the closest I have seen to it but am still unsure if that is correct.
Americana Chrome Ink Ball Pen Kit - Americana Classic Range - Pen Kits - Shop