Blackout/Marker/Tail/Stop light question

[Tony Smith]

I've seen a couple of variations in these lights on various vehicles. I've often wondered if there is any signifigance in the two designs, the "Acorn" style on the left, and the "Square" style on the right.

I have been told by various people that these are different because of:
1. Ford / Chev manufacture.
2. Early / Late production.
3. A matter of different subcontractors.
4. Who cares?

Can anyone shed any light (pardon the pun) on this bet winning question?
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