Phil: These seem to show up in Hallicrafters on an irregular basis. Perhaps
some were added by owners after production. Perhaps it was a question of
availability. However, I have encountered several that had a mixture of Allen
and Spline Bristol. Assume nothing! Be aware also, that Hallicrafters sometimes
used 2 set screws, one atop the other, as a lock. Especially common on larger
knobs. This tidbit will prevent destroying a perfectly good knob, pot, or
switch, in some cases! The larger hammer syndrome! Thanks, Wayne