Safari! Ethiopia #120-34, Set/15 On Real Photo Postcards

According to Scott, the difference between the 1919 stamps and their reprints is the gum. Since the gum on these can no longer be inspected, a bit of detective work seems called for. First, notice that these are all cancelled in 1931, very late usages. Second, the backs of the cards have no writing, so these stamps did not do postal duty, they're merely cancelled. Were the reprints even actually valid for postage? And third, and probably most telling, the 'printed but not issued' $2 stamp (#130) is in this group.
It's most likely that these are the reprints, readily available in full sets to tourists for years after the original stamps. Only four dates are present, from February to July, and three cities, beginning with the capital in February, then down the road east, ending with Harrar in May and again in July. Could it be that our friend the tourist spent these two whole months in the bush on safari near the Somali border, hitting the local post office on the way in, then again on the way out? Such a life...