NavList:

I rang the London Name Plate Manufacturing Co (in Brighton) and spoke to a lovely lady called Gloria who’d been there 50 years.  Douglas protractors are now only made in small batches, mainly for civilian use.  The covers went from cardboard, to grey plastic, and now to clear plastic.  The instructions are occasionally revised.  She had copies of the 1976 and Feb2008 instructions (the most recent).  She’s going to send me copies.  Both say ‘align with a meridian of longitude’ not ‘align with a meridian or parallel’, so it looks like the earlier instructions carried a longstanding mistake, possibly introduced in the rush to train rapidly expanding numbers of aircrew and naval personnel in WW2.

To finish this off, we ought to find out when the protractor was first produced?  What was the original transparent material, there weren’t many modern plastics around until WW2?  Was it Celluloid or Bakelite, or later Perspex, and did it stop clear very long?  Was the reason for the original stout cover to protect it from daylight or just scratching?  If it was inflammable Celluloid, bearing in mind the popularity of smoking in the forces and civil aviation, were there ever any unpleasant surprises?  Richard Dunn or Roger Connor might be able to help with this.  DaveP