Repairing a Lucas 25D distributor with a Bad advance curve

At a recent tuning session, this distributor was determined to be giving bad ignition timing.
Taking the unit apart revealed that someone had removed the primary spring. With only the secondary spring operating the advance curve, this car had approx 10 degrees of total ignition advance.
After cleaning, polishing, and greasing the internal parts, a new primary spring was sourced and installed. This was tested on my distributor machine to prove that the advance curve as in fact back to specifications.
Vacuum advance as well as total advance also checked.