Well, to find the ACTUAL build number you are going to have to talk to POS - I mean PAS. And since they are no longer in business you are pretty screwed. I have heard rumors there are people who have the documents saying what your EXACT build number is - but the information isn't for the general public to have. It has become an understood for the Ty owners to use the last 4 digits of the VIN. Most people just accept this is the way it is.