This is the nut that I had on my Warwick’s
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ah, mine were not spinning, just two screws, one raises from the bass side, one from treble. and they don't rotate by themselves. they call it Just-a-nut III (or I had the II? IDK). they make it both in tedur and brass and they look like this:
p.s. this design also allows adjusting them without loosening or taking off your strings