Due to the manner in which the Dynasonic frame barely kissed the bottom head, Rogers engineers made a slight notch in the D series Swivomatic strainers which gave the Dynasonic a touch more positive lockup vrs. the Powertone throw. Somewhere late in the dayton era, or possibly early fullerton, all Swivomatic throws were made the same and the D was dropped from the knob post. A Dynasonic swivo throwoff will function fine in a Powertone.

If you can find one! Bid for an original at your own peril. Buy a repro and be prepared to be scalped on price and postage. Curse all those idiots who lost/threw away the original frames! Good luck with it anyway.