Originally Posted by T-Mar

I'm almost positive this is not a Nishiki. The major contractors for Nishiki were Kawamura, Katakura, Giant and Derby. All stamped their serial numbers on the bottom bracket shell and circa 1978-1984, Giant stamped a date code on the left, rear dropout.

Schwinn stamped serial numbers on the head tube, but typically it was at the bottom. One manufacturer who stamped their serial number on the collar of the top head lug was Bianchi, during the 1970s and very early 1980s. The serial number format is consistent for the period, so I'd be checking the bottom bracket threading, to see if it is Italian.