Science, Technology and Engineering
Geralt
CC0 1.0
Gears
Steven Fine
Clock gears
Przemek Pietrak
CC BY-SA 3.0
Rods n Wires
Ben Salter from Wales
CC BY-SA 2.0
Skytrain abstract 1
Colin Knowles
Dorothy_Stevens-Aeroplane_Factory_Ready_for_Shipment
Dorothy Stevens
Public domain