Update on Colligate 3 Serial Number.

Thanks to the help of u/Alijony and u/Wakethesnakes . I was able to identify the bike's year, being from March of 1983. On the left side of the rear dropout is this Serial Number which searching gave me the date range of 8/19-8/21 of 1957, However on the right was the serial number G0383.

I'm just confused as to why this bike would have a serial number dating back to 1957.