Those of you who are familar with these radio's will have noticed this is a later model with additional upgrades, all the valves apart from the left hand side (half wave rectifier) are now fitted with B9A valve bases, using 6BE6, 6BA6 ,EBC90 and of interest the 6BW6 audio amplifier first introduced in 1950. The original audio output valve 6V6GT was first introduced in 1937, so as the first models came off the production line it seems possible that these were going to become difficult to keep production going. So perhaps within a year or so a new design was being developed and again costs in production could be reduced by the aerial . How many of these were produced i'm not sure as all the others I have seen or information on these sets only identify the first production model.