This is fascinating. From a web search, the American Chestnut Foundation has a formal process for submitting a sample.
On their request for samples, and why [0]: "Please let us know if you think you have found an American chestnut by submitting a Tree Locator Form and leaf sample. We are always looking to expand our inventory of chestnut trees across the native range. [...] "TACF is continuing its breeding program to make further gains in disease resistance and forest competitiveness, as well as forest health and restoration in general."
On how to submit a sample [1]: The foundation has developed a procedure where you can submit a twig, leaf, and photos to one of their representatives, to verify if the samples came from an American chestnut tree.
On their request for samples, and why [0]: "Please let us know if you think you have found an American chestnut by submitting a Tree Locator Form and leaf sample. We are always looking to expand our inventory of chestnut trees across the native range. [...] "TACF is continuing its breeding program to make further gains in disease resistance and forest competitiveness, as well as forest health and restoration in general."
On how to submit a sample [1]: The foundation has developed a procedure where you can submit a twig, leaf, and photos to one of their representatives, to verify if the samples came from an American chestnut tree.
[0] https://acf.org/resources/faqs/
[1] https://acf.org/resources/identification/