I went to Fort Campbell Boulevard today to get some goodies. I bought a black Magpul windowed PMAG with a date code of October 2008. The thing I noticed that was unusual was the number "2" was below the date code. I have several PMAGs and have never noticed this number before. What does it mean?

That's weird.  I have PMags with a date code of October 2008 but don't have the number 2 below it.  But, I do have PMags with a date code of August 08 and they have the number 2 below it.  The only difference I noticed is that the PMags with 08/08 and the number 2 on it will drop freely in any situation, loaded, unloaded, closed bolt, open bolt.  With the PMags that have a date code of 10/08, they only drop freely with a closed bolt.  Open bolt I have to pull it out.  There is no difference in functionality.  I don't know the real answer to this but this is what I have experienced with that number which I don't even know what its suppose to mean.

Mine has #2 Hell I didn't know they had a date code till I read your post.
I don't look at anything that close. I never was one of those little boys
that took things apart. If it worked. ..good, if not..take it back

Just what I figured. That damn DrDrake is not going to let us in on his little secret.

its an expiration date

Maybe it's like Willy Wonka... there's a gold certificate inside that gets you in the MagPul plant, where if you're good (and don't screw with the equipment) you'll end up owning the place!