Difference between our measured K magnitude (from photometric system calibration) and the predicted K magnitude (bandpass corrected from Schödel et al. (2010) Ks) for calibrators used in Witzel et al. (2012). The measured K magnitudes are consistent with the predicted ones, with an average difference of 0.01 ± 0.09 mag and a zero-point uncertainty ﹩{\overline{\sigma }}_{\mathrm{zp}}﹩ of 0.16 mag (dark band; light band: ﹩2{\overline{\sigma }}_{\mathrm{zp}}﹩). This verifies that the early infrared (IR) measurements made based on speckle images are on the same photometric system as the later IR measurements obtained from AO.