No puzzle. It's a 1979. The derailleur cable routing is above the bottom bracket, it has the rear cable stop bridge for center-pull brakes and the circular headbadge. In fact, if chrome was not covered up in the repaint, it is either an Omega or LeMans. With all due respect to your wife, the bicycle is definitely not from 1973-1976. The serial number and headbadge irrefutably place it from 1979.