While we are on this subject I might as well ask about something that has long puzzled me- the idea that some regiments had front turnbacks only. Where did this come from? You see it sometimes in SYW figure ranges, but I can't say I've seen any reference to it in any historical material. The closest reference I can think of is the Funcken "Lace Wars" book which shows loads of coats with the front skirt turned back, but it's a schematic drawing and I assumed the artist was just showing the lining colour of the coat.
It never made much sense to me anyway- the front skirt was held back by attaching it to the rear skirt which had to be turned over as well, so if the front one was turned only what would it attach to? I suppose there could be a button to hook on to, but I've never seen that. I suppose the turnback could be "false" i.e. just sown into the coat, but I don't think this was done in the French army of the time.
Perhaps I'm missing the evidence for this?