I spent the last day wading through this entire thread. Happy to say I'm a new first time Thiel owner. I found a pair of cs2.3 for $450 and after a bit of research snatched them up. One tweeter was dented with a small puncture but I was able to pop it out and "patch" the hole with a very small very thin piece of nylon film until I can foot a rebuild.
Unfortunately the serial numbers are extremely faded. I can't make out much at all but they appear to start with a 1. This doesn't really jive with the rest of the serial numbers I'm seeing online which appear to all range in the 4000's. Rob with Coherent Source told me the coax drivers were mainly manufactured in '99 and '00 but I popped one out and mine has a manufacture date of October '98. I likely have one of the earliest it seems.
Does anyone have any info on what the serial number range might have been for the cs2.3's? I assumed they started at 4000 based on what I've seen but perhaps I'm wrong.
Anyways, they sound fantastic. I'm thrilled with their sound.