Hi,
 
    In about two weeks there will be an interesting article published on
the origins and early history of, two-sided records.
 
  One of the few remaining puzzles is how Colin McKenzie got a Canadian
patent for the concept in Dec 1904, when Ademor Petit already had it, in
Canada: 75705 (1901-1902).
 
Thanks.
 
Allen
 (with apologies for possible cross-posting.)