Ad showing Corning CRT bulb glass plant
 

Ad for Mobil lubricants showing Corning CRT glass plant.

Note the text

This dramatic operation shows parts of TV tube
being joined on Electric Sealing Lathe. Edges of
tube parts are softened by gas flame, then
sealed by high frequency electric current when
glass becomes hot enough to conduct electricity.

I didn't know it was, or even could be, done by HF electrical conduction heating. They don't mention if this involves glass frit.