Reminds me that I was once (during a Test Match series) very popular at
school for having a home-brew 3-transistor MW/LW radio built into a
Woolworth's plastic sandwich box. Reason for choice of box? - It had a
circular vent grill exactly the right size to accomodate one of those
DLR earphone transducers used as a speaker. Quite a group of boys could
gather round and listen to scores etc. Also box could be installed
between a couple of book covers and carried around with other volumes
quite surreptitiously. Happy days!

P.S. Transistors in those far-off days were sold to little boys
 by colour-spot designation -not numbers like OC71 etc

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73 es gd dx de Pat G4GVW, Nr Felixstowe, East Coast, UK