I saw the documentary American Hardcore last night, and there was some grainy concert footage of Black Flag that showed their bassist whaling on what looked like a Spoiler.  It was one of the few non-P-basses I saw through the entire show...
 
I've so far been unsuccessful in finding any still pics of the Alembic in action with Black Flag, though.

I saw a live video of their Black Coffee once - their bassist looked very young and indeed seemed to play a Spoiler.