In 1956, Sun Oil Company (Sun Oil) (plaintiff) began using the mark Custom-Blended on blending pumps at Sun Oil’s gas stations. Sun Oil eventually attempted to register the Custom-Blended mark as a trademark, but the trademark examiner rejected the registration. The examiner viewed the mark as highly descriptive of the associated product, making the mark ineligible for trademark protection without a secondary meaning. Sun Oil appealed the decision to the Trademark Trial and Appeal Board (the TTAB), but the TTAB upheld the decision of the examiner. The TTAB specifically found that the Custom-Blended mark was descriptive as applied to Sun Oil’s blended gasoline and that Sun Oil had failed to provide evidence that the consuming public primarily viewed the mark as an indicator of source. Sun Oil appealed the decision.