These headphones are marked Dominion Electrohome Ind. Ltd. Kitchener Canada and my Uncle has engraved 6.5k on the headphone case. 

From what I can find Electrohome mainly manufactured radios in the 1940s?  and I assume these were supplied with a radio set?  He was a very keen amateur radio enthusiast and worked for HMV.  There is no way of testing as the clamp end looks like it would have been attached to a battery?    Listed as for parts as I have no way of checking whether they work.

If anybody reading this give me any more information of this item I would appreciate it as I can find nothing on the internet.  Thank you