I once had a 1980 Datsun truck that had two coils, 2 plugs per cylinder and a 10-wire distributor (2 in, 8 out). My understanding is both plugs were fired at the same time with the aim of faster and more complete combustion in the cylinder. I passed that truck to family in 1993 when I moved to California. Sitting in a cousins barn in Ohio, last I knew.