Folks,
Problem is arborists' names and foresters' names are not consistent with each other. Robinia is the black or yellow locust, has extremely fragrant flowers, (white) and seldom could make a mast at all (here in Missouri anyway) because of tendency to decay easily (while alive). I've NEVER seen a tree that oculd make a sawlog, much less a post.
Honeylocust (Gleditsia)is very durable, decay resistant and could make a decent post, if ever one could be found tall and straight. Maybe grown close together?
Both are legumes. Whatever else this "mast locust" is, it is probably a legume as well, but I doubt either of these two trees.
The earlier description of the thorns was accurate. The one with the brutal, long thorns is honeylocust.