Help needed on disassembling combination switch

["Hal Faulkner" <hal@katemuir.com>]

Well, while the half shaft is still broken (pending arrival of replacement
from Buster-I guess he really wants FROG AYE to be at the cluster) I decided
it was a good time to loose my last key.  Now how the heck does one get the
old cylinder out of the combination switch to either take it to a locksmith
or simply replace it?  I see a pin in a hole through the black knob just
opposite the word "off" but pushing it in doesn't seem to release the knob.
What's the trick?

Hal