I'm a new member and have been searching this site for Jeffries Duet info.
I have a 51 key Jeffries Duet that I bought back in the 80s, not aware at the time what it was, but it was too good a price to let go. When I did find out, I was determined not to have it 'converted' but kept it as a duet. I play it occasionally for Morris, though not very well!
It has the same address as Malcolm's instrument in the oval (with 'Jeffries Bros Maker' but without the word 'LATE') and has 'C. J. NEW ADDRESS 12. ALDERSHOT ROAD KILBURN N.W.6' under the right handrest - although, on my instrument, it is poorly stamped as, rather curiously, the 'N' in NEW, KILBURN and N.W.6 is reversed!
Paul