I am working on installing a 19AP4 in a dumont 109. Question--- the HV
brass contact is improperly installed on the old tube and needs now to
be reinstalled properly. Is it supposed to be contacting the rim of the tube
Or to the metal bell.

Electrically, it doesn't really matter. The whole metal bell is at the same potential. Physically though, there should be a plastic shroud over most of the bell, leaving just the rim of the tube exposed. The clip should be at the rim.

As i thought, thanks