1Ж42А. As a mixer/Frequency changer????

[Mike Watterson]

So the 1J42A appears to be effected by magnetism.

Yes. It's mentioned by Joe Sousa on the Radiomuseum articles and in the Russian literature. It's a pair of precision low power electron beams, in wedge shape. That's why the Russian stuff usually has tinned steel rather than copper or aluminium screens.
I use cut up Lidl coffee tin.