i'm going to crawl out on a limb here and take a guess that you probably have one of the first ones. I do remember when they first came out with the MIB contols on those and it was about that time.. 1999 to 2000, give or take a year or so.
BUT.. if you do want to know for sure you will have to call yale ;)
or maybe someone's memory serves them better than mine that can remember for sure.