Dining chairs with interesting joinery  

No ID(ea), but you get extra points for correct joinery nomenclature.

At first glance, I would guess American 1970's-'80's. Wood species, fastener types, upholstery, and other details would all be clues. I wonder if the wedged through-tenons are actually clever little inlays covering screws. So many on one chair is an awful lot of finicky work for an otherwise unremarkable set...

I'll take the points! Otherwise, I completely agree with everything you mention. I've even considered that they could be a woodworker's home project. I can't figure out what manufacturer would want to execute all of those joints on one (very boring, rectilinear) chair!