loupe

luppi, luuppi A magnifying glass, usually mounted in an eyepiece, often used by jewellers and watchmakers.
1996, (w), Infinite Jest, Abacus 2013, p. 213:

Pemulis owns stuff like philatelic forceps, a loupe, a pharmaceutical scale, a postal scale, a personal-size Bunsen burner ….

pale gnomes, patient as lock-pickers, squinted through loupes, adjusting tremblers and timers with tiny screwdrivers and forceps.