These are either employee or giveaway items from a Nintendo competetion. All of these came from a "Jollyrancher" ebay auction. I think the jersey was a staff uniform for the day and the ball and cards prizes for the winners. I bought this lot for around $100 a few years back. and about a dozen of these.
I'm pretty sure that KG baseball card came packaged with the SNES title (Ken Griffey presents: Major League Baseball). I know I had one, and I didn't subscribe to any gaming magazines back when it was released.
Heh, when I first read the title I thought this was about a sequel to 300 ;D Cool stuff. I'm kind of sure I've seen that baseball card before, wonder if it was in some old gaming magazine.
I think the thread title being "600" is in reference to the fact that Griffey just hit his 600th career home run the other day. i must also say that i think the card came with the SNES game, because i have one as well. But i was also a Nintendo Power subscriber at the time so it could have come from there.