[Ron Ramirez]

Yes, there were. Earlier single 47 model 90s have two cylindrical shields; one over the 27 near the back center of the chassis, as you described; the other over one of the 27 tubes near the 47 and 80. Later versions of the single 47 chassis have the flat piece of metal in between the grouping of four tubes (27, 27, 47, 80) near the Mershons and the power transformer.