In January, 1920, Ernest Clark opened the Clark Orchestra Roll Co. in DeKalb, Illinois.  Clark took over the production of coin-operated rolls from QRS and continued to supply rolls to Seeburg under the name "Automatic Music Roll Co."  -- Art Reblitz in 010202 MMDigest.

As you may know, Clark had an agreement with QRS by which Clark got a copy of every QRS master, which Clark transcribed for their various nickelodeon rolls.  Before 1923 or 1924 Clark used QRS masters but also employed their own arrangers to make special nickelodeon-only arrangements of certain songs.  After about 1924 Clark never again made any of their own arrangements and used QRS masters exclusively.  -- Dave Junchen in a letter to Art Reblitz, published in 020122 MMDigest..

Clark rolls with black border labels are the later ones.  When Clark Orchestra Roll Co. was incorporated in 1920, times were good and the labels were printed in two colors, with black lettering and red borders.  During the Great Depression of the 1930s, sales declined to the point where C.O.R.C. was making very little money.  One way the firm economized was to print the labels in one color -- black.  The printing was done by Ernest Clark's son, Bayard, who had a print shop in the same building.  -- Art Reblitz in 080513 MMDigest
 

Many tracker scales and key frame layouts are included in "The Golden Age of Automatic Musical Instruments," copyright 2001 by Arthur A. Reblitz, and in "Treasures of Mechanical Music," copyright 1981 by Arthur A. Reblitz and Q. David Bowers.