This trail in summer when there is no snow and the rock is good is nothing more than a class 1 or maybe 2 scramble (haven't even seen it in summer). However in mid to late winter, when there are no trail markings the last section of trail to the summit of Mt. Mansfield is clearly Class 3 (crampons required, ice axe strongly advised). Keep in mind that the summer foothold are not there and you are at the mercy of how stable the snow is. One fall could result in a fall of hundreds of feet. When I was there I never even saw footprints in this section of trail.