As a result of some further 'surfing', I have found that Sonoretta Radios were made by
'Elektra' in Czechoslovakia in the 40s & 50s. They are listed both on
http:www.radiomuseum.org *and
www.radiohistoria.sk. Both list an earlier model, the RV12, a 2-valve TRF, which I have also seen, but neither list the 3 valve superhet which is the subject of this thread. What caused me some confusion is that the word 'Jiskra' is molded into the inside of the Cabinets.
* Although the URL I've quoted for the Radio Museum site is correct, for some reason a '404 not found' page is displayed when clicking on it, and I don't know why