My OCD required that I check into this a little further, and I dug this up:

Sennheiser Electronics Corporation MD 421-II | RecordingHacks.com

I couldn't verify the claims here, but it says the MK II came out in 2002, and that the gold special edition was released to celebrate Fritz Sennheiser's 90's birthday, which, according to another article I found about him, would have also been in 2002. My thirst for virtually useless tidbits of information is now satisfied. (for today)