"BC" is a hum bucking coil. I've seen the primary resistance of these transformers read from several hundred to around a thousand ohms. The secondary will generally read less than 1 ohm. I believe
www.tubesandmore.com sells a universal output transformer designed for these old radios. Usually, these transformers will simply open up on their own. Just to be safe, I'd replace any caps in the audio circuit and I'd make sure the output tubes were not shorted. If in doubt, replace the tubes.