Distributor Clamps and Micro-Adjusters
Here's a photo of all the distributor clamps I have.
Top left is the TA, TB, and TC clamp with micro-adjuster. The adjustment range is 2 degrees advanced to 8 degrees retarded. 8 clicks per degree of adjustment. The markings are stamped into the barrel of the adjuster. The center shank of the barrel is brass.
Top right is the Triple-M clamp without micro-adjuster. This was used on all Triple-M cars that did not have manual advance nor a magneto. The one shown is home-made.
Bottom center is a clamp that was on my late PB. Note that it has a micro-adjuster, but also has the same fixing bolt arrangement as the Triple-M clamp. Does anyone know its source? The adjustment range and precision is the same as the T-type adjuster above. The markings on the barrel are raised and somewhat finer than the T-type adjuster. The center shank of the barrel is steel.
Notes for all clamps:
The plate was held down with a plain hex-head bolt.
The clamping screw was a slotted, cheese-head screw 1/4" coarse thread with a thin lockwasher and hex nut. The insert direction of the clamp screw is open to debate, but would appear, on the PA, PB, NA, and NB, to be inserted so that the nut is closest to the dynamo.
And these (below) sent from a well-respected authority in the UK.