[Arran]

I would try something like Evaporust, or a similar product, there is a guy on Y.T that does this with aluminum fined tuning condensers and it doesn't seem to harm those. If you want to try vinegar mix it 50:50 with water, for some reason I find it works better at stripping rust then straight vinegar, if you want it to work faster heat up the mixture, since the Philco ones are all steel there should not be a problem. I did run a tuning condenser from a 40s radio through the dishwasher, it did not turn grey but it was spotty afterward, I would not have tried it except that the aluminum plates had scale on them, it did take the scale off.
Regards
Arran