Rob - I have likewise not heard of any high 2.7 serial numbers. Rob gave me the 1500 pair figure and I take it on his word. I do know that by that time Thiel’s export markets were stronger than domestic. We’ll see what surfaces as time goes on.
Yes, that 400uF electrolytic cap in the midrange feed is not Jim Thiel - never done. As a fly on the wall, I gathered that there were ongoing struggles between Home Team Thiel and Warkwyn who ’knew best’. New ’finalized’ samples would come from Toronto with persisting failures to honor such requests. When their tab hit $250K, Kathy pulled the plug and began production. New Thiel didn’t deem it worth the trouble to make future changes.
Regarding 3.7 vs 2.7, I see almost every value changed for the 2.7. Circuitry layouts are similar in that the same basic resonances are being compensated. But there are significant differences and no shared component values between the three models' crossovers.
I’ve heard the models 3.7 and 2.7 only once at Thiel’s music room September 2012. I was overjoyed by the performance of both, especially the 3.7. What a Swan Song.