Evening gents - yup thats crystal set No4 from the Boys book of crystal sets , I too was intrieged with this set quite liked the idea of using both sides of the antenna coil , made a few different versions to see how it could made to work better - a couple of pics of the biggest version which has sliding basket weave coils with a hand crank which moves the coils , center coil stays there , two larger ones are the tank coils so there are three antenna coils in series and when you wind the crank the outer coils move twice the distance of the tank coils due to larger pulley sise keeping the tanks central in-between the antenna coils , the coupling bevel gear driving the tuning cap rotors has a sliding clutch so as to offset for maxamising output was a fun build and works quite well , sorry she's a bit dirty at moment
cheers Dunk
P.s. - included a pic of the original circut from the book that suckered me into this hobby :)