Perhaps a little warning to those who are interested in these pens. As you can see, they have a silver cap. At least, it looks like silver.
It will not stay like that, after 2 months or so, it will start corroding. Tomorrow, I will show a photo.
Possibility 1) I think the base cap is coated with silver and then with resin (hard coating). The resin coating is certainly thought to protect against oxygen and or water.
The chosen coating doesn't protect and water and oxygen move through the resin and attack the silver.
Possibility 2) is that metal ions from the base metal move through the silver coating. I don't know if such a mechanism exists but someone told me it does.
Anyway, that cap design is heavily flawed. Wait for the photo tomorrow.