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We propose UV spectroscopy of the supermassive black hole binary (SBHB) candidate J095036+512838 (J0950) to test the alternative scenario that it harbors a perturbed accretion disk around a single black hole. By analogy to spectroscopic binary stars comma this object was originally selected as a SBHB candidate by virtue of the virgul1300 km-s blueshift of its broad Balmer lines relative to the rest frame set by the narrow lines. According to new spectroscopic monitoring of the radial velocity curve comma J0950 recently passed conjunction and is consistent with a SBHB with a period of order decades. This is an extremely strong indication of binary motion that no other candidate has shown before comma making J095036 the strongest candidate of its class. The radial velocity curve also conclusively rules out the hypothesis that this is a recoiling black hole. We will observe the Ly-alpha and C IV broad lines to discriminate between the SBHB hypothesis and the single comma perturbed accretion disk hypothesis. In the former scenario the UV lines are expected to be offset in velocity just as the optical Balmer lines while in the latter they are expected to be centered at the redshift of the narrow optical emission lines.