Barcode wand
The pen-shaped reader you dragged by hand across a printed barcode — the simplest of the early scanners.
The barcode wand was the cheapest of the early scanners: its tip holds an LED and a photodiode, and as it sweeps a code the reflected light alternates between bars and spaces. The electronics time those transitions rather than measure widths, since the operator's swipe speed varies from pass to pass.
That is exactly why self-checking symbologies like Code 39, tolerant of uneven speed, mattered. Wands were common in warehouses and libraries through the 1970s and 80s but lost out to contactless laser and CCD scanners, which read at a distance and never abrade the label.