In checking 4 phones with confirmed CID's of 15, I see: 14.05, 14.04, 14.06, & 14.05.
I've found this to be a reliable way of getting a phone with a CID of 15. HOWEVER, I have come across a phone with a code of 14.08 and a CID of 11, so it seems that 14.08 is for sure the cut off, and that...