From what I've read, this does not seem like something we send. Seems like an internal record that is created by CIS/CBP to record the creation of an LPR record for someone. Typically after a 485 approval, entry of a CP-approved person for the first time into the country and so on. I see a few references to it in the adjudicators field manual, indicating that this document is created internally. I dont know though if it is available to the external world. Perhaps more knowledgeable forum members may know.
HTH