Change-over to Sealed Beam Headlights in 1940

In 1939 US auto and truck manufacturers realized the following year would be the introduction of the revolutionary new, we call them "almost" sealed beam headlight bulbs.  These first "almost" seal beams were very unique by the newer standards 15 years later that most of us are acquainted with.  This early sealed beam assembly was much like the later design except it had a much smaller 2 filament light bulb inside.  Yes, the inside reflective plating was sealed inside with a glass fluted large lens that was now part of the total assembly.  This reflective coating was sealed from outside air and oxidizing did not occur.  There was no loss of shine with age.  It was one of the best improvements in safety since the introduction of bulb headlights.

A very interesting characteristic of these first "almost" seal beams:  A small hole from a flying rock did not burn out the unit.  The argon gas that protected the glowing filaments from quick burn-out was still inside the small internal bulb.

Real seal beam bulbs introduced in the mid 1950’s were different.  They were one large argon filled assembly.  When cracked by a flying rock, they instantly burned out.  Imagine the number of new designed sealed beam bulbs that were lost by vehicles driving at high speeds on gravel roads behind other vehicles!  There must have been a run on the old style obsolete units in rural areas.

The later 12 volt sealed beams were not made with the early design “small in the reflector” design.

For most car and truck manufacturers it was too late to do a major redesign of the headlight assemblies for the 1940 year.  Chevrolet and GMC trucks reshaped the metal edge on the 1939 bucket so the new seal beam bulbs fit perfectly.  For those not having a detailed eye for auto and truck changes, it would probably never be noticed.

For those buying a new 1940 vehicle after driving with the old style reflector bulb design, it would be the most significant change in years.  The gradual diming of their lights over the years as the silver reflector tarnished was now history.  Yes, the owner could have removed the glass lens from his older vehicle, the very lightly polish the silver plate, and reassemble. However, it would be likely most drivers would not take the effort.

Below are photos of the earlier 1937-39 headlight and the new 1940 redesigned for the new seal beam.  The visible part of the buckets is identical including the chrome rings.  It’s only the hidden edge for the "almost" sealed beam bucket that is different.