[Arran]

The paper filter caps in these sets, and A.Ks were not oil impregnated, but they apparently used a higher quality paper then the paper caps you typically run into in sets from the mid to late 1930s, plus the potting material does a good job of keeping the moisture out. In my opinion I would not trust 80+ year old paper caps no matter how good they test, even with voltage across them, age will degrade the paper dielectric if nothing else. Besides that the can not only has the paper caps it has most of the bypass caps in it as well which can also fail.
In short using the set as is is like playing Russian roulette (my apologies to Morzh) if you play on using the set on a regular basis. I have a Westinghouse model 89, a 1929 set with big block condensers, and while the filter caps have not shorted out the set does not work, in short they still need to be replaced.
Regards
Arran