Bob,
Thanks for the pics. I just grabbed the Autolite filter and included it in the picture as an example of a more traditional style. It has a C5AZ-9155-B engineering number so am assuming it is a service replacement? Not sure where it fits in. The total hex Rotunda body filter does have a C5AE-9155-A2 engineering number. I can't find a date code on the nut, or anywhere else, on either filter.
I have several other filters ink stamped in red with a C5AE-9155-A4 like your pics but have Autolite instead of Rotunda. Again no date codes that I can find. They come in Autolite star logo C5AZ-9155-B boxes. Any chance these are assembly line correct for later (March) 66? If service replacements what time frame would they fit in?
Thanks,
Dave