Can you give any more info on this bike? What components aside from the 105 brakes does it have? Are the dropouts stamped with any names? Is there a tubing decal on the seat tube and/or fork blades?
I admit to knowing absolutely nothing when it comes to Puch/AD serial numbers, but for what it's worth my Puch Mistral from 1982 has a 7 digit serial number that begins with 65, so if they numbered sequentially during manufacture, yours might not be that much older. But like I said... don't know squat.

Photos would help a lot too.