Portriga Speed was one of my favorite papers before Agfa went bust.
It's a graded paper and you are correct that this is what the big "2" is for. In this case, this pack is Grade 2.
Before VC paper you used to match your neg contrast to the paper and that would mean you might have umpteen different boxes of different grades. Same principle now, except one box does it all and you just change filtration to increase or decrease contrast.
I've used some old paper on several occasions in the Postcard Exchange and more often than not, the paper was fine.
Enjoy experimenting with it - if it's still ok, you've scored some lovely paper.