Mazda RX7 strut cap. (I'm told that it is also called the Upper Tray Hook Lock, although that seems like a weird name).
This is a replacement for the decorative cover on the back deck of the RX7. My friend brought me a broken one and I made this for him. It fit well. He painted his to match the original.
My friend said the part is FB67-56-353. His car is the 1988 model FC2 body style.