When Data/File based workflows started in movies (around 2004), 2-3 copies was the standard from the get go and ideally this was with MD5 checksums (currently xxhash is more common because it's alot faster). LTO backups are also generally part of the copy chains as the 3rd or 4th copy. Before that, duplication with tape was while recording wasn't as common, but it was more common to duplicate after recording. Although you'd have some amount of generation loss depending on the format, not so with recording to multiple decks with the same source video. With film it obviously wasn't possible but original negative (o-neg) was much more cautiously handled. You'd have copies made going to an interpositive for editing and dailies process. Those wouldn't an identical quality so to get a negative copy, you'd be 2 generations of loss. By the time you're seeing a print in a theater, it would be 3 generations. (one->IP->IN->print)