Thanks Dr Drew,
That’s interesting about the Armbrust ballistic tests in the 1930’s. One would assume that there would be much more consistent results by the 80’s and 90’s, when I think most of these older 209 primers were made. As for the other, non-Herters primers, I just today, came across this information below in the Alliant 2023 re-loading manual.



This seems to help clarify two of the older 209 primers (Remington and Federal), classifying them as normal and not hot. If I read this correctly.