A friend showed me a weird flanged nut today, still trying to figure out
what it was. Approximately M12 diameter, coarse thread, flanged nut,
think it was used in a Porsche. Starting from the flange side, there
were approximately 5 regular threads, a gap with no threads at all bored
out to the major diameter, and then one complete thread. It looked like
a standard nylon locking nut with the nylon removed and with a thread
instead of the top crimp.

What is it???