They’re fascinating. They are all set reference photos – pictures taken of sets by the MGM art department during shooting for the sake of continuity or for record keeping.
Some of the pics make for striking photography in and of themselves. I saw one sequence, for example, which were various angles of a scar on a horse’s neck – special fx make-up, not a real scar. They’d been photographed by the MGM art department on some horse-racing movie for their own continuity reference. But they were very strange images – like insurance photos carefully taken of a victim, except that the subject was non-human, and photographed on high-quality 8×10 black and white negs.