When we picked up our Safari in Oct., 2008, I saw those indentations in the Marathons and asked about them. We went looking at other tires on the lot and there were some Michelins on bus style MoHo's and they had the indentations too. I figured if they are on Michelins, they must be ok. No one at the dealership knew anything about tires, a reassuring experience.
I never looked to see where the Marathons were made since some ignorance is perhaps a good idea. I did look at the date and it was mid 2008. I think we're over 15,000 miles and no problems, tread looks good, and next year if we go to Alaska, I will change to better tires.
If you don't see weights on your wheels, look at the back—that's where they may be.
Interesting about dots and wheel notches—I never had to think about all this stuff before I got a trailer. I can't wait to be at a campground and impress someone with all this information.