French makers have had very different steel suppliers, changing with the vagaries of war and peace. France lost Alsace-Lorraine in 1871, recovered it with the 1919 Versailles Peace Treaty and occupied Rhenania and the Ruhr in the twenties. When they had the choice makers used steel produced in the Ruhr or in Sheffield from Swedish ore.
For vintage blades it's important to note that HT wasn't as reliable as it is nowadays. You may find poorly treated blades next to an exceptionally good one. The difference might be due to a cigarette and a glass of wine at the right or wrong moment,
My thin carbon Gyuto don't like to cut frozen fruit wt. for smoothies.I use a elephant carbon santoku.It is a sturdy little cutter.Even wt. frozen fruit no chipping & holds a good edge.I bought it about a yr. ago have put it to the stones a# of times,sharpens up well.All this makes me feel like it is quality carbon wt. good HT made in France.