How about a thread for references on the colored lens dots that fuel so much speculation? No claims without citing sources, please.
A yellow dot indicates the use of synthetic thermosetting cement instead of Canada balsam for extreme temperatures per this Army Technical Manual, pages 9-7 and 9-8.
A red dot indicates a lens has been treated against fungus growth and corrosion per this Air Force Manual, page 110.
A purple dot indicates anti-reflection coating per this 1947 B&L ad in International Projectionist.
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