I have owned a few of these sets .
Just after the war , the Wireless Institute of Australia ( WIA ) purchased a bulk amount of these, I believe it was around 400 sets . I have seen the surplus advert in the 1947 newspaper regarding the sale of these sets. These sets were then offered to hams , most hams were WIA members, at a bargain price. The WIA magazine published a article in 1948, how to make a AM modulator for the sets , I have that magazine .
A friend here has a set he wants to sell , so look on epay soon if you want a spy set . I was paying 100 bucks for them , but that was in the 1980's . Now whats the going price , thousands I would think
They still turn up.