Panasonic RQ-542S

The Panasonic RQ-542S is essentially the same thing as the National RQ-542 with some notable differences, which are that it has a different cosmetic trim, standard FM tuning range (compared to the RQ-542 which is 76mhz to 90mhz) and 120v capable as compared to the RQ-542, which is 100V as it's a Japan domestic only model. See that model to compare.

The service manual for this product can be purchased through AnalogAlley