I have to correct my own post here above^^ because yesterday while I was in work, I saw an old pic of a S64E Skycrane which was the bigger 7 main blade version. So apparently there were also S64E Skycranes which were the higher lift 7 main blade models.OK, to add to my post above^^ I just realized that the Skycrane shown here is an "S" model, which means that it's commercial rather than military. That explains why I've never seen that model before. The ones I've seen are bigger, more heavy duty, and have seven main blades because they are the military version. Just as our Blackhawk copter designated model 70, has the S70 version which was intended for commercial use rather than military as most of our Blackhawks are.
As I recall the army had a bunch at Ft Sill near Lawton in the late 70s. You could see them from the highway when passing by. I was stationed at Wichita Falls and then Altus and could see them when going up to OKC.