Here's a bit more info.
This particular stereoscope lives in my apartment and has been in the family for well over a hundred years. It's a little beat up, but that's only because it was well used. Back in the day, I'm told, they were commonly used by courting couples as a way to sit close together without alarming the chaperones.
Um, anyway. I originally meant the doodle to be a lot more detailed, but once I'd done the initial line drawing (slightly skewed perspective and all) I decided to keep it simple.