It's a Master Oscillator coil / tuning unit for a T.1083 WW II RAF Transmitter... think Lancaster. Two coil units (one square, one round) are used per band. They are VERY nicely built, but not really useful. There are detailed pics of mine on the RoyalSignals.org.uk site, -John > 110039229278 > > > Jay KE6PPF h.net/mailman/listinfo/arc5