Engineer wrote:
snip
Thanks for all replies. Yes, it's paper! The dielectric is super
thin, brown, translucent (likely impregnated), skin-like paper with
very low tensile strength - I did not test for burst and tear but will
certainly be low!
I plan to replace all of these that are under any B+ stress before
further restoration. I'll be using modern 0.12 uF, 630 volt, black
plastic, rectangular caps (Korean made.)

Everything I buy from Korea is checked very carefully.
If I were you I would replace all those tubular paper capacitors with
the wax on them. I found some that the leads had come loose and you
could twirl the capacitor while the leads were still soldered into the
radio.
Rare original IF's saved, Scott... and lessons learned!
Cheers,
Roger

Best of luck.
Bill Baka