From my point of view, Orville's Mark II was the first practical model rocket. The first rocket he made, Mark I, looked like fireworks of the time. So, I'm guessing, he wanted to get away from that look and made the Mark II. That would make the Mark II the first model rocket that looked like what we think of as a model rocket. That is, in my opinion, what makes it historically important.
On the Ye Olde Rocket Plans site,
there are 2 good copies of articles about the Rock-A-Chute rockets. One is about 9 down "09/58 Rock-A-Chute Aerobee-Hi Review"
the other is farther down after the Estes stuff, "10/57 Rock-A-Chute Article"
These show some photos. Also see the article in Sport Rocketry in the July/Aug 2007 issue. It's about a build of the Mark II using an original Leeds Sweete plastic crayon sharpener. Some of the information that the modeler used in the Sport Rocketry article came from Bill Stine at Quest. I am hoping that this information will be a part of the "The Model Rocket Museum" mentioned in this forum and on the Quest website.
This is also one of my interests right now, as I too have an original crayon sharpener to use as a nose cone. A buddy of mine re-created the Rock-A-Chute logo for me to make a decal for the rocket. I'll post it here for all. I will be posting that build, along with an 3X upscale build of the Mark II, hopefully in a few weeks.
Somewhere on this forum, I read that someone had talked to G. Harry Stine and said he had bought a Rock-A-Chute Mark II as a kit sometime in the late 50's I'm guessing. So, this would mean that Orville kitted the Mark II and maybe sold some locally from where he lived. That would make the Mark II the first rocket kit ever sold. I love this history stuff.