The base is a set of chem lab safety goggles, wrapped in leather from last year's cowboy costume. Pretty much everything is hot-glued on. I love hot glue.
The eye-rims are flashlight caps spray-painted gold. The lenses in them are from an old LCD screen.
I put computer case screws into the sides of the eye-rims, and hung a chain from one of the screws.
For the monocle, I had a round metal piece with a shaft, and another scrap that fit on it like a lever. I hot-glued a bushing with some lens material to that, and put other pieces around it to hold it in place.
On one of the eye-rims I glued a nut, with a tube coming out of it and into some bulbous scrap. From there it goes into a brass doorstop where it is routed with a gold(-sprayed keyboard cable) tube to the other side of the goggles (for barometric balance). I later (after these pictures) put a line of unmelted solder on the bottom to outline it.
You can check out the Instructable for the Gatling gun arm now!