Texas Instruments Naming Scheme for Scientific

I am well versed in the progression of TI graphing calculators, but have been trying to make sense of their scientific calculators naming scheme or product lines. I had a TI-34 in elementary school. Then there was Ti-34ii, which makes sense as both a sequel as well as the ii standing for 2 lines. Then there was Ti-34 multi-view. Makes sense.

But they also went back to ti-30, and TI-30ii, and then TI-36X. Does X stand for the 4 lines of text like Multi-view? Is 36 a different product line or TI just wanted a bigger number? But then the replacement for the TI-36X is back to the TI-30 Pro.

Categorizing all of these is difficult, or being able to look at a product name and defer to what its features are. Looking at http://www.datamath.org shows just how many different models there have been.