For the proof of the genuine Hitachiwagyu Beef provider, Ibaraki Hitachiwagyu Beef Promotion Association issues the certificate for designated restaurants or retaillers and wholesellers.
In Japan, all the Hitachiwagyu Beef farmers and the traders are registered to promote and uphold the standerds for Hitachiwagyu Beef.
Not only the production side, the retailers and restaurants are registered as a Hitachiwagyu Beef official seller.

*Designated buyer:  the buyer who is authorized to attend the wholesale market
*carcass:  carcass is the meat which is slaughtered, removed skin and cut off head and internal organs. Normally
  they are cut half (right and left). The designated carcass are graded and sold at wholesale meat auction followed
  by the carcass trading system standard.

  For confirming the traseability check this link(English only)  http://www.id.nlbc.go.jp/english/