Hi all, I have a Sekai 1500 mixte and I'm trying to identify the correct year. My girlfriend rides the bike daily and it is in great condition. A few upgrades have been made and I'm eventually going to overhaul and upgrade the entire bike. Any help in identifying the year would be greatly appreciated. Thank you!

Here are the specs:
Sekai 1500 Mixte (made in Japan) Serial: Y0L7327
-Tange High Carbon Standard Gauge tubing
-Sugino Cranks (doubled) stamped with "Sugino forged Japan 165" on each arm, the left arm also stamped with 'J-9' and the right arm stamped with 'J-11'
-Front derailer: Suntour 7 (stamped 4532)
-Rear derailer: Suntour 7 GT (can't read the stamped markings, will try again after cleaning)
-Shifters: Suntour stem friction
-Cassette: 5 speed
-Brakes: Dia-Compe Center Pull stamped with 'Drop Forged' on each brake and the following numbers: '0177' and '610' on the front brake arms and '5583', '610' and '0280' on the rear brake.
-Handlebars: SR (Sakae) 'North Road' mustache-like bars
-Stem: SR (Sakae)

My best guest is probably 1983. The numbers on the brakes are misleading though. I'm guessing they used a mixture of parts from different years to assemble the brakes. I could not successfully identify the Suntour components looking online or on the vintage trek site. Nor could I find anyway to decipher the serial number. Any clues here? Thanks!

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