I have 2 Pelikan ballpoints sitting in boxes in a drawer for more than a few years (one is a K650 and the other is a rare K850, both Gold). Pictures attached. I noticed a brownish, reddish discoloration on the bottom of the caps. I spoke briefly to a man at the Fountain Pen Hospital who told me that it will come out easily with a cleaner. Anyone familiar with this? The pens are both in great shape but I don't use them much anymore. I was even considering putting them up for sale here.