I don't have any doubt this is a Klein. All the details are right. Schwinn aluminum used a monostay above the rear brake, Cannondale has the "dented" stay to clear the chanrings. Klein used that front derailleur a lot, kind of one of the signature features of a Klein in the mid 80's. I'm not sure when Klein went to the top of the down tube arrangement, but 1984 ads for Klein showed the side of the down tube shifters also. I think 1984 is accurate.