The diff's are subtle.
Generally the French knives are a little thinner and a little taller at the heel. Look at the French Sabatier lines of knives there are a few. Also the German are full tang and many of the French, but not all, are through tang handle.
The one that most of the French culinary knife snobs love is the four Star Elephant Satatier in carbon steel. The seller claim these were from forgings made prior to WWII, I am not sure that's really true??? German lovers are a little more mixed. With some of the brands there really isn't any noticeable difference between the German or French except as I mentioned the French seem to run a little thinner and maybe a little taller at the heel as mentioned.