Wikipedia
Keykode
Keykode (also written as either KeyKode or KeyCode) is an Eastman Kodak Company advancement on edge numbers, which are letters, numbers and symbols placed at regular intervals along the edge of 35 mm and 16 mm film to allow for frame-by-frame specific identification. It was introduced in 1990.
Keykode is a variation of time code used in the post-production process which is designed to uniquely identify film frames in a film stock.