Pictures to go with. The last three look similar but are all slightly different (even though one is broke).
Watch for this - the middle one has the part that holds the screw broken off. I've seen them like this several times now - I bought this one at a small junk shop, didn't realize it was broke, but it came with an extra cam set so I still got it for a good deal. I don't think it is required other than to keep you from losing the mounting screw.
