Proper-motion distribution for cluster members (red circles) and field stars (blue dots) in the field of Stock 2, NGC 1960, and FSR 866, derived on the basis of membership probability. The probability threshold for membership is 0.95, 0.95, and 0.985, respectively. Proper motions are from Gaia DR3. On the second panel, that corresponds to NGC 1960, two concentrations besides the cluster are visible, and are discussed in Section 2