From Photo-Lab-Index, page 16-04:

"Prints are also suplied by Eastman Kodak Company. Three sizes are made from 35mm and Bantam transparencies under the name of Minicolor prints, and a large number of sizes are made from Kodachrome Professional films under the name of Kotavachrome.
Kodak Minicolor prints are enlarged from either 35mm or Bantam sized Kodachrome transparencies by a standardized process in the Kodak Labratories in Rochester. They are made only from Kodachromes in 2 x 2 mounts with the standard central openings. Enlargements are avaiable in three sizes. The '2X' is about 2 1/4 x 3 1/4. On these the corners are rounded and there are no margins. The larger size '5X' affords a print 5 3/8 x 7 4/5 and prints are returned in mounts--for horizontals, 8 3/8 x 10 1/4 and for verticals, 8 3/8 x 11 9/16, the picture opening, or area measuring 5 x 7 1/2. The largest size, '8X', is approximately 8 x 11, and is returned mounted in a folder.
The quality of a Minicolor Print naturally depends on the quality of the Kodachrome transparency from which it is made. A good properly exposed transparency whic will project well should yield a good color print.
The 'feel' of a Kodak Minicolor Print, particularly in the smaller size, is that of a playing card, strong, attractive, and resilient. The print support, or base, however, is not paper or card, but white pigmented cellulose acetate.
Kotavachrome Professional Prints are reproduced from Kodachrome Professional Film Transparencies and must be made by Kodak Laboratories by the Kodachrome process in the following sizes: 8 x 10, 11 x 14, 14 x 17, 16 x 20, 20 x 24, 24 x 30, 30 x 40. They will be made from all sizes of Kodachrome Film Transparencies except 45 x 107mm 6 x 134cm, and 11 x 14 inches. The maximum enlargement from any transparency is limited to six diameters. Transparencies may be cropped. If this is desired, it is necessary to indicate clearly by an overlay accompanying the transparency.
Duplicates of transparencies, either enlarged or reduced on film, are also supplied by Eastman Kodak Co."