Other than the one in our collection, we can only find references to two others. One is in the ICL Computer Museum. There is also a record of one being sold at the Historic Tech website but it may have been the one that appears at the ICL Computer Museum.
For more information, click on the link(s) below.
     ICL Computer Museum with pictures

     Historic Tech Site

If you know the location of any other of these, please let us know by contacting us at info@EarlyComputers.com.