Mid 30's 16h

This is mine. 1937.

The threaded brake rod is 9/32 × 26.  The proper wing nut fits into the lever. This one is from NOC spares but was 1/4×26. Drilled out and threaded 

The frame shown in the original post looks to be a 1940-on WD16H item, with both field stand and pillion footrest lugs. This shouldn't though affect the rear brake operation.

There were two types of WD16H rods, the early version being identical to pre-war civilian and the later introduced to allow adjustment at the front once the rear was obstructed by the military pannier frames.

In both cases, the operating arm should face upwards as per David's,  with the torque arm fixing to a stud on the brake plate which sits underneath.

The original large bronze wing nut has a rounded nose which acts as a detent in conjunction with the rear curve of the brake arm. The half-round spacer was used in conjunction with the later set-up, as it was simply locked in place with a nut.

It looks as if you may have a mixture of earlier and later parts. Footrest arms and brake pedals too vary between military and civilian, not a problem if they are fitted as a set.

Richard...I can't work out what the small lugs beneath the rear chain stay, one at the front and one at the back, are for.  Did they ever have a full rear chain case?  Or perhaps plan one?  The Dommie has similar, but threaded and smaller.

The lug at the rear is a mirror image of the silencer mount on the other side. Presumably all the rear drop-outs (if that bicycle term is allowable) were twin-port compatible.

At the front is the stand cross-tube...but on the WD machines, surplus to requirements as a fixture.

That makes sense! Thanks.  When I'm bored enough, I might go and see if rear lugs are indentical on both sides, or mirror image.

.. why they chose an odd size like 9/32"? To be honest when I made a rod for my ES2 I used 1/4".

My guess is to sell more genuine Norton spare parts!  I scoured Kempton jumble from end to end, new and old - and bought the only 9/32" tap there was.

Tracy tools stock the taps and dies.