Doohickie

Thanks for the plug! The picture you show is a classic style mixte. I have seen some (which I still consider a mixte) that have a single top tube that goes to the seat tube following a line drawn from the top of the head tube to the rear dropout; at the seat tube it becomes a pair of twin stays (to make a third set of stays along with the chain stays and seat stays). To me, having the third pair of stays distinguishes a mixte, whether or not they extend all the way to the head tube or they and at the seat tube and continue as a single tube to the head tube. (For an example of this variation, see Rivendell's Betty Foy.)