Also there's more to the proper replacement headset then the threading standard, or the frame/fork fits. It's the stack height. A lot of lower cost steel headsets have a fairly minimal stack height. To find stack height measure the "thickness" of the lower and the upper units or the overall fork steerer length minus the head tube length. 33-42mm is the typical range for a threaded unit.

So the needed dimensions are the fit to the fork crown and head tube, the threading and the stack height.

I was going to mention that Peugeot had changed from French dimensionally specd bikes to Eng/Jap in the late 1970s but started with the upper end bikes first. The CFX-10 is not a base grade model so I figured that it was Eng threaded.

I will add that headsets are one component that many don't fully understand all the compatibility aspects, or don't take the time to find these out before buying. This is one area where the LBS can often save time and mistakes. Andy