From Nodak? You have one advantage over most of us. No hills. I remember a group of riders from North Dakota who came to Wisconsin to participate in a race. They said they used highway overpasses to get even a hint of a hill to train. They were no match for the steep hill at the end of the race. As I recall visiting Grand Forks that the change in elevation might be as little as a foot per mile. That proved devastating when the Red River flooded the "new" Grand Forks high school in 1997 even though it was really far away from the river bank.
You can read a little about the Simplex name here
https://en.wikipedia.org/wiki/Lucien_Juy. I haven't seen a bike with Simplex derailleurs since the 70s. They were made in France like your bike. The company has been gone for a third of a century. Be aware that French bikes have French threaded parts and are not the same as English threads. The Japanese were wiser to adopted the English thread system making their parts compatible with many European and American bikes. I'm surprised to see you can still get French threaded parts for the BB and headset online.