There is a 49 key Jeffries duet up for auction on eBay and there are some nice pictures of its ends:   http://www.ebay.com/itm/261752151748?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT   Looking at these pictures I can see how Brian Hayden got the idea for his button layout for the Hayden system. It would be very straightforward to map a useful version of the Hayden system onto the existing buttons on this box.