[Hallicrafters] SX-100 Notch Freq & Depth Knobs

[jsloss]

Did Hallicrafters ever use a small knob, numbered 0 - 10 over 360 degrees, with 4 small division lines between each digit?  I have a SX-100 with these knobs for Notch freq  & depth and am trying to decide if they are factory original.

Would also appreciate knowing approximately production date of a SX-28A S/N 53170 and "SX-28A" on the panel which is in line for restoration eventually.

Thanks

Joe k7mks