Close-up Week - Image 1

OK. It's close-up week. Each image this week will be a close-up of an object whose identity may not be immediately obvious. See if you can work out what each image is showing and post your answer in a comment. I'll list image identities at the end of the week (SUNDAY).

An easy one to start with but see if you can come up with the specific item!

Olympus E-3; ISO 400; f - extension tube; 1/320s; 60mm.