Wide Flute vs Narrow Flute Headlights

[TWS]

When did the factory switch from wide flute headlight bulbs / lenses to the narrow flute?  Thanks!

[TWS]

   bump

[70vert]

Just curious, what even is a headlight bulb flute?
Never too old to learn, right? 

[HP2]

Flutes are the little ridges cast into the glass to disperse or concentrate light. Didn't know they had a formal names, but it makes sense since they are cast and not cut like a facet.

I always thought low beams had more or more varied flutes than high beams. Don't know how or when the factory changed this, even they even specified it. I'd think they were at the mercy of evolving technology by the lighting providers.

[Mr Cuda]

 When you drive your numbers matching,  bias ply tires, stock restored car, you need the mellow glow from your wide flute sealed beam.
Otherwise,  you need halogen to see.
I think they changed in 72-3 to narrow  flute. Right before the first rectangle bulbs of 75 - 6.