Common proper motion plots for those candidates with archival astrometry. The black line indicates the predicted path for a stationary background object, which is measured relative to the first archival epoch for HD 176638, and relative to the second epoch for HD 182681 since the first epoch is inconsistent with other early measurements. In each case the orange, green, and blue points indicate astrometry from Wahhaj et al. (2013), Galicher et al. (2016), and this work respectively, with darker points being measurements and lighter points being the predicted background position at each epoch. For HD 176638 we see a small offset between the astrometry reported in this work and that from Wahhaj et al. (2013), common in comparative astrometry between different instruments with their own systematics. For HD 182681 we see broadly good agreement between all epochs, albeit with significant scatter between the earlier measurements. Our astrometry is consistent with previous works, and with each of these candidates being a background source.