Seems like it didn't find its way onto the internet - except for an advertisement that says it has additives to make whites whiter. I'd use it, though. Grade 4 and 5 survive the years well, in my experience, although it might need btz or potassium bromide in the dev to cut the fog. Or maybe you could lith print it. It will probably be slower than new paper.
If those spots are there only when wet, it might be ok. Aslo, sometimes the top sheet is bad and the rest are better. But spots are generally a bad indication. The only way you'll find out about its lith capability is to try it, I think.
I was able to make a contact print of a 21 step wedge - it worked but the grey spots are still there on the dry paper.
I used a paper from an already opened box, hopefully the paper in the other 5 (still closed) packages is better.