I have a bottom end Nishiki Olympic five speed freewheel. It has a serial number KS 286901. It has a cottered crankset, Shimano Tourney GS RD, Shimano 50 FD, stem mounted shifters, Dia Compe center pull brakes, Araya 27-1 1/4 steel rims, with Shimano hubs (quick release). It is a 19 inch frame, women's style. I would guess mid 70s. Bolts on crankset are marked "American Flyer". Bike is in pieces right now.

Update: I cleaned the bike up and reassembled it. Now it is off to CL for a new home.