Top panels: Rotation curves and best-fit sinusoidal for both GCs. The bottom panels show the location of the target stars, colour-coded by radial velocity in units of their dispersion. Diamonds refer to M 75 targets on chip #1 on FORS2, circles indicate stars on chip #2, and MIKE targets are shown without extra delimiters. The gray shaded areas indicate the error margin of the rotation axis, which itself is shown as a dashed line. The major axis PAs of each cluster from Chen & Chen (2010) are plotted as thin red lines; finally, the direction of the Gaia DR2 proper motion is shown via a thick red line.