Interesting! It seems almost like these were assembled somewhere other than the factory as the 391 manufacturer date code goes back to WWII. Even more head scratching is they were still building the 'A' with an 'Iconic' label, 811 horn as late as '56. This still doesn't explain the difference in vent design as the woofers should all be pretty much identical through this period.
I presume these have N-800-D XOs.
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