[Arran]

 I don't know what Philco models would have contained electrostatic speakers, if any. The only electrostatic speakers that I have seen were tweeters used in late 1950s and 60s European built radios and combo units and those were no where near the size of that thing. To me that unit looks more like a large appliance part of some kind, possibly from an air conditioner, maybe it's an electrostatic filter rather then a speaker? It looks like it would fit around a blower housing.
Regards
Arran