I have a architectural shingle with a very strong shadow line about 1.5 " wide and the only other marking is on the plastic strip on the back side ( do not remove Y12 ) It's not Elk, Tamko, GAF, or Owens corning. massive granulation loss and cracking after 8 years. I live about 50 miles north of Kansas City MO.
I don't know the answer; not sure if any of the following manufacturers were in business 8 years ago: Mansfield, Byrd (spelling?). I hope you asked Building Supply Companies in the surrounding area.
You don't and that's the plan. Even if you determined the manufacturer, they'd deny a claim by simply claiming they weren't installed correctly. And, the only way to even have "a chance" in forcing them to honor their warranty would be a lawyer, lots of money and even more time. Corporations (non-people) mean more than their customers (people) is the moral of the last century's story. A recall is just a super-cheap bailout to silence all of the preyed-upon victim whiners.