Joined: Jan 2008
Posts: 23,639
Likes: 1,106
From: Mans of NC & SW UT Desert
Bikes: 86 Katakura Silk, 87 Prologue X2, 88 Cimarron LE, 1975 Sekai 4000 Professional, 73 Paramount, plus more
+100 The Suntour stuff will have date codes. Seat post and handlebar stem will both have date codes. I have also found codes on diacompe brake calipers and levers. Crankset could be original, but the bike might still be a 1976. I usually add six months to the newest original part date code.
You are certainly pretty close, late 70s.