This auction is for 10x 5mm banana sockets. These appear to be zinc plated (but I am not sure). They can either take a banana plug or they also have a small hole where a wire can be inserted and the terminal screwed down to hold it in place. See the pics for more information.

I have not been able to source these anywhere so it looks like this type may not be made anymore. They are well built, unused and high quality.

When originally purchased, these would have been quite expensive so grab yourself a deal.