convex lens
Spur Gears.
Converging lenses are usally uses on cameras as they act as a magnifyer.
This has nothing to do with science-fiction but in former decades Sperm oil- yes from the Sperm Whale was used to lubricate fine watches and other scientific instruments. It was also part of the...
A loup
The small magnifying lens used by jewelers and watchmakers is a loupe.