The 425 number is 750 and model, it's part of the complete part number. '425' means DOHC 750. 73(0) is the last digits in part number meaning C model. The other number is likely numerical as in seats made to identify, the 804th seat in a batch.
Seat entire part number is 77200-425-730, the 77200 points at seat assembly. Part number is 'seat-750-C model'.