Subpanel wired directly to service conductors?

Older panel from the 1950’s…there is a subpanel nearby. The feed to the subpanel is wired directing to the service conductors on the main panel…The subpanel has a main disconnect on it…90 percent sure this is not allowed but want more feedback…your thoughts?..(orange and black wires at top are the feed to the subpanel)

Incorrect wiring, hazard needs immediate repair by a qualified person… Roy