Hi, I have an Apple Performa 550 that I've wanted to sale. I know they're not worth much but I was looking at the specs online and noticed something. The introduction dates on multiple sources for the 550 say October 1993. Here's the thing, my Performa 550 says (September) 1993! Does this mean anything? Is mine rare? I'm not trying to jump to conclusions, I just don't want to miss a good opportunity!