A very clever illustration with just a bit of color.
Gears of all types go well in themes of:
Masculine, Mechanical, Vehicles, and all types of Transportation as well as Steam Punk themes.
From: The Wellcome Collection
©: listed as under Public Domain w/ CC mark 1.0
CC Mark 1.0 info can be found here
https://creativecommons.org/publicdomain/mark/1.0/
