Electron Microscope Mystery 5

July and August are incredibly hectic months for my programs at NSF, so I have been a major slacker here at FS. To make up for it, I bring you a new electron microscope mystery! The field of view here is 6mm. What do you think it is?

Update, Wednesday August 8, 8:40a: This seems to be a difficult one! So here’s a second image, same scale, of the other end of this object. A hint: Many of us depend on a bunch of these, daily!

Update, Saturday August 11, 4:40p: Well, this proved difficult for everyone I spoke to, on and off this page. Here’s the answer: It’s a link in a bike chain!