I'll vouch for the 1.2 as being the first second-generation Thiel speaker. It preceded the CS5 and as such was the working trial for our first copper motor shunts, and aluminum dome tweeter. This was the first product to benefit from our investment in Finite Element Analysis. And it shows.
The CS1.2 is one sweet speaker as is, plus it lends itself very well to XO component upgrades.