> Slapfight A76 rom labels was released first (as a prototype or very limited release) > on a green PCB (Toaplan) for the Japanese domestic market and should be the parent > set in MAME. > Slapfight A77 on blue Taito PCB was released afterwards in Japan for the domestic > market and also in the USA as Alcon on the blue Taito A77 PCB.
By MAME rules A77 should be the parent. MAME marks latest/most widespread release as the parent.