I don't think I'd call that a mixte. Maybe a hodge-podge wannabe mixte pound puppy. I usually like Ahearne's style, but I think he was making a bit too much use of his flasks when he designed that.

Atleast Ahearne makes real (and purty) mixtes. Scroll through the gallery until you see the detail of the seat stay.

http://www.ahearnecycles.com/galleries/Maggie/index.htm