Interesting comments. Was checking LaBaron Bonnets site and found reference to this for AD models . I believe they base their kits on original samples they gather. Caused me to wonder if ALL models were had this, specific years or models?
After research here and reading your comments, IF they were standard equipment wonder why's there is sparse actual info about them? Also you logically would conclude that more samples, examples, info would have survived these years.
I know this is perhaps trivial. But you would think there would be an irrefutable answer to this existing----SOMEPLACE?