The paint on the loco is looking a bit battered, must get a hard life on the exhibition circuit.
The coil for the rear coupler is fitted above the gearbox. The long rotating operating rod goes above the rear wheel, and a bit of neat bending at the end of the wire forms the hook for DG couplings on a wagon. The operating rod has various bends in it to clear bits of chassis.
The DCC chip is fitted below the socket; a socketted arrangement was used so that the loco can be rapidly swapped back to analogue operations with a blanking plug (though will loose the remote control of coupler).