Here's a Sekai that I bought recently:

Serial: Y4A2427 (indicates 1984?)
Model: Magnum GT (same as the "Magnum S7" on the front page model listing?)
Cranks: Sugino GT 110/74
Wheels: aftermarket 700c, Sun rims

This one's Norco-branded on the seatstays, has Sekai decals on the headtube and downtubes.