I disagree that I was one of the last Sigs bought though. I upgraded the Sig list in February 2012 from my April 2010 production reservation of P2407. Timdorr's list shows about 130 Sig sequence reservations after me (1313). If there truly were just 1000 Sig cars, my vin should have been in the 870-940 range instead of over 1000, wouldn't you think?
As mentioned, I'm 10 sequence numbers after you and my VIN is 1049, so you're right in line. I've asked for clarification on the VINs -- while I don't really care that my VIN is 1049 I'm curious as to why it is so. In May I was told it was "highly unlikely" that I'd get a Sig spot, and about 2 weeks later I got a call -- so until they started dealing with other cancellations, you were probably one of the last Sigs.
My theory on the last (130+) Sig numbers is that they're very sparsely populated, almost as if just being on the waitlist meant a number was assigned to you, and they fell off quickly when time came to pony up the extra $35k. Just a theory.