having trouble with this, and have the brief instructs from io.com,
which i think are from the hro 50 instructs. have removed two set
screws which are accessed thru a hole in the black knob part of the
dial. turn the dial to 250, and have some play -- it moves back and
forth on the shaft for about 1/16" of an inch but does not come off.
reluctant of course to pull hard. there does not *seem* to be a catch
or some way to release from the back side, nor any other screws.

this is a somewhat unusual set of about nc-100 vintage (1939-41-
ishmade for precursor to FAA). has the sliding coil tank, and
receives usual shortwave bands plus an old airband. knob is black,
dial is grey. can't get the faceplate off for redo until dial knob
removed.

have original docs, but instructs for this not given there. bama, etc
no go for further docs on this unit.
ab.