A more recent analog is the Bi Lock from Australia, US patent numbers 4,478,061 and 4,498,327. See http://toool.nl/images/f/f9/Cutaway1.pdf page 15. It's unlikely the blanks would be close but I thought it would be interesting to point out the similarity. See also http://www.bilock.com/ and http://www.bilock.net/. At least the concept is still alive.