Ric
The construction of your radio has a very Philips look to it. The speaker in a cloth bag and the rectifier standing on top of the mains transformer are very characteristic of Philips designs. Also, the use of two ECH21 valves and an EBL21 to give a full superhet using only 3 valves plus rectifier was a Philips innovation that was also adopted by Tesla and others, see here
http://www.staff.science.uu.nl/~tel0...s/FourTube.htm
I wonder whether Sondyna were a Swiss subsidiary of Philips, or otherwise received technical assistance from them.
John