Martin did build guitars for other retailers, teachers, and musical instrument distributors; unlike Harmony´s or Kay´s house brands, though, "retitled" Martins were the exception and not the rule. If any of these trademarks are spotted, here´s a partial hint to origin:
Bacon Banjo Company: Around 1924, Martin supplied a number of guitars without Martin stamps or labels. However, most of the Bacon-trademarked guitars were built by Regal (Chicago, Illinois).
Belltone: Only a few Style 3K guitars, mandolins, and ukuleles were built for the Perlburg and Halpin company of New York City, New York.
Bitting Special: Both guitars and mandolins were built for this well-known music teacher in Bethlehem, Pennsylvania between 1916 and 1919.
Briggs Special: Sixty-five specially trimmed mandolin models were built for the Briggs Music shop in Utica, New York circa 1914 to 1919.
C. Bruno: Long before they were acquired by Kaman Music, C. Bruno was associated with C.F. Martin in 1838. Guitars carry a paper label that says "C.F. Martin & Bruno." Later C. Bruno & Sons guitars were not built by Martin.
William Foden: Concert guitarist and teacher William Foden had his own series of Foden Specials built by Martin. These models were primarily sold to his students between 1900 and 1920. Foden´s insistence on a twenty-fret fingerboard is now a standard feature on Martin guitars.
J.A. Handley: J.A. Handley was an instructor in Lowell, Massachusetts. He is credited with the development of the Style 6A mandolin.
Jenkins: This dealer in Kansas City, Missouri sold Martin ukuleles, renumbered #35 (Style 1) and #40 (Style 2).
Montgomery Ward: Martin had a short term deal with the Montgomery Ward company circa 1932. Martin supplied mahogany guitars, flat mandolins, and ukuleles.
Vahdah Olcott-Bickford: Vahdah Olcott-Bickford was a well-known concert artist and teacher. Guitars built to her specifications were called a Style 44, or Soloist.
Paramount: Paramount ordered about thirty special resonator models under the Paramount logo. Paramount was well known for their banjo models, which were not Martin instruments.
Rolando: The Rolando trademark shows up on a series of Martin-built koa Hawaiian-style guitars ordered by the Southern California Music Company (circa 1917-1920). Records also show a direct sale to J.J. Milligan Music.
Rudick´s: The Rudick´s firm of Akron, Ohio ordered a number of OO-17 guitars with the number O-55 stamped inside (circa 1935).
William J. Smith: The William J. Smith firm of New York City, New York had Martin-built ukuleles, taro patches and tiples in stock circa 1917.
Stetson: W.J. Dyer & Bro., known for their association with Larson Brothers acoustics, also specified three guitars for their Stetson trademark circa 1922.
S.S. Stewart: Distributors Buegeleisen and Jacobson of New York City, New York ordered ukuleles and other stringed instruments with their S.S. Stewart label circa 1923 to 1925.
John Wanamaker: The Wanamaker department store in Philadelphia, Pennsylvania ordered special models circa 1909.
H.A. Weymann & Son: The Weymann firm of Philadelphia, Pennsylvania was known for their banjos; Martin built a number of ukuleles and taro patches models around 1925.
Wolverine: The Wolverine trademark was applied to Martin-built guitars and mandolins for the Grinnell Brothers of Detroit, Michigan. Wolverine instruments carry the regular Martin serial numbers.
Rudolph Wurlitzer: The Wurlitzer music store chain ordered special model guitars between 1922 and 1924.
Information on "Retitled" Martin instruments courtesy: Mike Longworth, Martin Guitars: A History; Walter Carter, The Martin Book: A Complete History of Martin Guitars, and Tom Wheeler, American Guitars.