  An asteroid family forms as a result of a collision between an impactor and a
parent body. The fragments with ejection speeds higher than the escape velocity
from the parent body can escape its gravitational pull. The cloud of escaping
debris can be identified by the proximity of orbits in proper element, or
frequency, domains. Obtaining estimates of the original ejection speed can
provide valuable constraints on the physical processes occurring during
collision, and used to calibrate impact simulations. Unfortunately, proper
elements of asteroids families are modified by gravitational and
non-gravitational effects, such as resonant dynamics, encounters with massive
bodies, and the Yarkovsky effect, such that information on the original
ejection speeds is often lost, especially for older, more evolved families.
  It has been recently suggested that the distribution in proper inclination of
the Koronis family may have not been significantly perturbed by local dynamics,
and that information on the component of the ejection velocity that is
perpendicular to the orbital plane ($v_W$), may still be available, at least in
part. In this work we estimate the magnitude of the original ejection velocity
speeds of Koronis members using the observed distribution in proper
eccentricity and inclination, and accounting for the spread caused by dynamical
effects. Our results show that i) the spread in the original ejection speeds
is, to within a 15% error, inversely proportional to the fragment size, and ii)
the minimum ejection velocity is of the order of 50 m/s, with larger values
possible depending on the orbital configuration at the break-up.
