Does anyone know the vintage year and specs (efficiency rating) of the
Pioneer CS-99a speakers ?

I've had about 10 pairs of different vintage speakers so far- and these
by far have the heaviest cabinets and thickest board used to make the
cabinets- they also have removeable backs which is a nice plus. As
usual, finding info on these on the net is difficult, as most places
want to sell you a vintage audio "bible" to get the info.

any help appreciated- thanks