Try buyee. You can switch over to yahoo Japan via that service. Some items you are still not able to buy. I don't use it much, more knowledgeable people may be of more help.
None of these ebay sellers "own/possess" these items. They are for sale on yahoo Japan(for much cheaper)After a westerner pays double the price for them on ebay they purchase the item and have it sent to the buyer.
I've been seeing this done a lot by Japanese dealers(especially on ebay) my guess is they're taking Hazuya or Jizuya stones to rusted blades. I don't understand why they do this.
I'm assuming the top one is as ray said. The bottom may very well be the same.
Here's another in a mueseum. Looks like remains of a pin through the nakago to hold the tsuka on.
May just be the photos, but this looks like a separate piece:
I'm thinking the kabutogane comes off via the barrel screw, and the metal tsuka "cover" slides off and there's a hidden mekugi?