I tried some of this paper from Fox Run Kitchens. Billed as "parchment style, non-sticking lining for cooking, baking and candy making."

Claims to have "maximum temperature 425F without time limit."

Made in China
Fox Run Craftsman, Ivyland, PA 18974

I baked some bread on it at 425 (my oven fluctuates 10F +- so it was as high as 435F) and it stuck. I used a potato peeler to get it off the bottom crust.

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Switched to Beyond Gourmet Unbleached Parchment Paper. Product of Sweden. AV Olssuon Trading Co., Inc, Stamford, CT 06902

I have been able to bake bread up to 460F with no sticking.