The Orion (or O1) was killed when the manufacturer discontinued the CPU. I know TT stockpiled some at the time... that's under the original ownership, of course, not the current group of shmendricks... but sooner or later, they were going to run out.
The Orion II (O2) replaced the O1 with a lot of improvements, minor and major. The big difference was that the O2 had the newer CPU that replaced the discontinued one. And then, a few years later, the same thing happened. Now, why TT didn't come out with an O3 is another story.