Thank you. Maybe someone used the bark to write to someone they knew. Or a squirrel used it for a nest. So many possibilities, so few..barks? These trees are beautiful, and the moss/algae makes them even more so. At first glance, the tree banding in your photo looks almost made-up.

We have some river birch in the area that have darker brown bark, not as good for letter writing, but gorgeous colors for photography/painting.