Hamilton purchased the Illinois Watch Company in 1928 - not the best of times to take business risks considering the soon to start Great Depression. The Illinois Watch Company was a premier American watch brand, just like Hamilton, and it made perfect sense to bring two premier watch companies together. Hamilton made a good go of it for several years but eventually they closed the Illinois factory and moved all they could to Lancaster, PA. By the mid 1930s the Illinois brand was retired.
Decades later, the watch industry continued to evolve. WWII decimated Europe and the global economy overall. American watch companies began to falter. The market was shrinking. Price pressure came in two forms - the need to cut costs to make watches more affordable to customers AND the need to cut costs to compete with the high quality, low cost Swiss and German watch manufacturers. Sounds familiar.
Hamilton executives realized they needed to change their ways. For example, Hamilton NEVER used rolled gold plated cases until the mid 1950s. Their dials were always sterling silver and when markers were used, they were solid gold. How could they introduce cost cutting measures without risking their status as America's top watch producer?
I guess you could say, if you can't lick 'em, join 'em. They decided to purchase partially completed Swiss-made movements called an ébauche. Instead of a gold filled case, they used rolled gold plated cases with stainless steel backs. Dials could be embossed (stamped) instead of using applied gold figures. They decided to test the market and reintroduce the Illinois brand name since Illinois was still recallable as a quality manufacturer, and if the market imploded it wouldn't harm the Hamilton brand.
Several new models using the Illinois moniker were introduced in 1953 - including the first Automatic models and calendar models that Hamilton ever produced. One of the manual winding models was the Debonair Model B, or Debonair B, as it would eventually be called.
The Model B was produced through 1955, at which point Hamilton executives dropped the Illinois reference and Hamilton-branded models with Swiss ébauches were introduced.