It used to a Gitane Tour de France from the early '70s. I got in '75 and used it as a road bike for years.
But over the past many years it just sat.
So I did a fixed conversion. Really, I got a flip-flop hub, so if I regain my senses I can go single speed.
So far, after seven miles, I can report that riding fixed is weird. Really weird. The riding itself is fine (the old steel bike feels great.) I haven't been bucked off, but I have been kicked a couple of times when I foolishly tried to coast. Trying to stop is interesting. Even with brakes it feels awkward. Going downhill is a special kind of oh-no-thrill.
I'm relieved to find getting started is not bad at all. I think I rode so long in toe clips that it getting my feet in just happens.
I'm going to try commuting a bit on it and see if I learn to embrace it, as so many have. I'm may find that I'll fine my knees are too old, and I'm too set in my gear-changing ways to adapt. Or maybe I'll just become super cool.