I've heard from machinists that 10.8 means it was made in Taiwan or China. Don't know for sure, but I do notice the U.S. bolt companies online and the better hardware stores sell 10.9
Since fasteners hold things together that people trust their lives to, there is a lot of control and controversy over the cheap Chinese fasteners floating around and how to avoid them.

Don't know the history, but I notice 8.8 is pretty standard everywhere you go, but when you get up into the quality, more critical bolts, you find the out of sequence 10.9 and 12.9. It figures that it is a way of letting people know it's the good stuff. I can't imagine why else there would be a grade system of just .10 difference created.

At any rate, I've never heard of stainless hardware rated 10.8 or 10.9. That's a rating for carbon/alloy steel bolts. A2, A4 and the like is how stainless is rated. Sometimes 18-8. Stainless is not that strong, just corrosion resistent. It's generally used as marine hardware.

Perhaps someone out there can provide more.