Hi. If they are the ribbon tweeters that I think they are, they were very high end. A small box, slightly trapozoid type shape. Very heavy rare earth magnets.
I am pretty sure that they were used in The Mark Levinson stacked Quads/Decca London super system.
A friend of mine had some here in Perth, Western Australia in his Magnapan Tympani system. They were awesome.
Peter