Actually, despite the title, the telephones in question here are somewhat before the era of Blondie!
The vintage high impedance headphones I purchased arrived today. They are in surprisingly good condition considering their age, and the repair mentioned in the sale listing is actually quite well done. Theres no fabric on the headband, but the fabric covered cord is in good nick. They are marked BTH BBC.
So far, I have tested these using a meter on the resistance ranges, the small current causing them to crackle - and I can hear that crackle in both 'receivers'. I cant read the resistance though, I suspect because my meter is rubbish! But, I can hear noises from them, which is what they are supposed to do.
Next trick is to get some audio into them, but I want to protect them from excessive DC (the winding wire is very thin!) so will rig up a small audio transformer to feed them.
Im hoping they will work nicely with the Pixie transceiver. I'll see about that tomorrow.