Hello,
That is one sweet hat. I have no information on the milliner. The hat style could be 1930's, or it could be post WWII, late 1940s early 1950's. It is hard to tell...can you show it on a head without the big hair? Can you show the inside of the hat? The graphics on the label show a lady wearing a hat from circa 1939-1945, but it is possible that the hat itself is later. If Mathilde had these labels in stock after WWII, she likely may have continued to sew them into her hats until she used them up. The velvet looks like silk velvet. Is it a heavy and very dense velvet, or is it a thinner lightweight velvet? That can actually help in dating.
One more question...what is that little jewel thingie hanging off the end? Is it rhinestones, or maybe crystals? If you can show that close up it is another very good clue.
I really love that hat, it is a rich color and appears very well made.
B