Why aren't the early to mid-nineties RX-7 badges the familiar Mazda M on the RX-8 and Miata, or the rotory looking thing from earlier RX models? What is the significance of that weird little design? I think I've seen them on other Mazdas (the early MP3 and the earlier Miatas?), but I can't figure out why they almost look like an "o" shape.

it probably has some zoroasterian significance

ahura mazda=god of light and mazda namesake

All Mazdas from that time had the badge with the "o" in it.

I like referring to the badge with the o inside the circle as the "toilet bowl". BTW, I heard that somewhere else, I can't take credit. I am not a fan, so I changed to the efini badging.