Inspection of the front looks like a little piece of ND plastic is missing from the photoresistor opening. No problem, plenty of graded ND available in old control strips.
With a little trial-and-error, I found a piece of film with a density to exactly match the response a newer flash, known to produce acceptable exposures. Linearity is good without having to adjust the internal trimmers; 3ft, 6ft, & 12ft flash distances demonstrate the appropriate 2 stop drop.
Last edited by ic-racer; 09-16-2013 at 08:07 PM. Click to view previous post history.