As an example, my Thiel CS 3.7 serial numbers are 87 and 88. I don't know how many pairs were sold in total, but obviously it was one of the earliest sets built (I had 7.2s before that). I have a couple of pairs of old SCS2s (for side and back surrounds in my integrated AV system) and the serial numbers are worn off from those. I also have an MCS1 center channel and a pair of the original Power Points for front height channels. I bought one pair of the SCS2s used (the customer of the store died and they were too beat up for them to take in trade so I stripped off the beat up black ash and painted them the color of the walls. At one point in the old house, I had that pair of SCS2s hung on the wall (with Ominmounts) as left and right channels in the bedroom. I've also owned 2.3s and when my friend worked in the stereo store for about 6 years I help deliver and set-up a bunch of different pairs (mainly 1.6s and 1.7s and 2.3s and 2.4s). When I decided to upgrade my 2.3s, I was on a business trip in the Palo Alto, CA area and was fortunate a dealer there had all the Thiel models on the floor and they were gracious enough to let me spend time comparing the 6s and 7.2s for quite a while so I could make up my mind.
