I can't give you an answer regarding the prototype markings.
But I do believe that the crank is a Centaur MTB rather than Olympus. Compare the area around the mounting bolt hole and there is a difference: Centaur has a small angled area in one section and Olympus has no angled section.
https://velobase.com/ViewComponent.a...=115&AbsPos=16
https://velobase.com/ViewComponent.a...66c4d&Enum=115