<VV> Utterly Dead Electrical System LM

[Kent Duncan]

My '65 500 has gone completely dead electrically.  No starter, no headlights, no idiot lights--nothing.  It's been sitting several days, so the battery's down to reading 12.5 V, but I get that same voltage reading at the engine compartment harness connection (checking the red #10 gauge), the under-dash harness connection, and the ignition switch itself.  Pulled the ignition switch and the continuity seems to be correct in each key position.  I don't know where to go from here--what am I missing?
 
TIA
 
Kent Duncan