[Arran]

The square ceramic object is most likely a padder condenser, which is for the tracking on the lower end of the dial, in some sets they call it a "600 padder". This temperature compensating device is certainly an oddity, I have run into zero temperature co-efficient caps in some Rogers built sets, but not one that intentionally varies with temperature, not in an 89 year old radio. I would guess that Philco must have have produced them in house as I can't recall seeing them in anything else, on first glance I thought maybe someone was playing around in there, I've seen chokes and other things added before to try and quash some interference, or sub another defective part. Someone was doing that with the antenna coil, either the primary is open or someone was experimenting with it in some way.
Regards
Arran