SkyDog75

You've got an early-to-mid 1970s Peugeot UO-18. It's essentially the mixte version of the ubiquitous UO-8.

1972 is plausible. To confirm, you may be able to find date codes stamped into the Rigida rims or on the back side of the rear derailleur cage between the pulleys.

The single shifter boss on the frame is original. Like Aubergine mentioned, a lot of lower-end Peugeots were equipped with a single shifter boss. The shifter for the rear derailleur mounted to this boss. The shifter for the front derailleur mounted to a band, and the right-side boss kept the band from slipping. The SunTour shifters on your bike are definitely not original, so maybe a previous owner decided to switch from downtube shifters.

As for restoring the bike... Let me first point out that I really, really like my '72 Peugeot UO-8, which is a lot like your UO-18. It's a very comfortable bike to ride and it's got some vintage character. But with that said, these bikes had a lot of shortcomings as originally equipped. Since these bikes don't have any appreciable collector value, it's not a major faux pas to sacrifice some of the bike's originality for the sake of practicality and safety. You can make changes and upgrades using period-correct parts or tasteful updates that fit the character of the bike, while making it a better bike to ride. First and foremost, the Delrin (plastic) parts that get brittle with age are candidates for replacement. The front derailleurs almost always have broken clamps. The rear derailleurs aren't quite as fragile ...unless you count the pulleys. The Delrin downtube shift levers were flimsy even when new. Delrin brake levers?! Yeah, I like playing Russian roulette with my brakes. "Maybe this will be the time the lever snaps... Let me squeeze it and find out!"

<EDIT> And just because they might as well be cousins, I've attached a picture of my '72 UO-8. I've since replaced the saddle with something more appropriate and I've got a nicer looking crankset that I just haven't gotten around to installing yet.