I'm pretty sure that the IP used for the DC masters was used to replace parts of the o-neg for the "new" SE negative. However, since it was a negative being made, those segments would have been duped from the IP, leaving it intact in itself. This was the first generation IP from the original negative, which is why it was chosen for the DC masters (at the time it was considered the best single source). Why it was chosen over the dye-transfer print (which was also struck from the o-neg) I don't know. Which is in better shape now is another question. However, it seems there are at least two good 2nd generation sources intact.