It looks to me like that cabinet has been modified somewhat. The hinges to the compartment cover on the left, appear to be the original hinges for the cabinet top. There were other special hinges on the compartment cover below the top hinges. The machine head originally folded down into the cabinet, lifted back up, and was held in place by the top extension leaf that your cabinet is missing. The movement was accomplished using a cable and pulley system attached to the leaf. The cable rested in a groove in the wood on the back left side of the cabinet. The folding action on yours is being held in the raised position without the chain lift somehow.
CD in Oklahoma