The employing agency is responsible for establishing its own procedure for obtaining an appraisal that represents the value of the gift in the United States. This applies to all gifts, even when the recipient wishes to retain and/or purchase the gift. Appraisals are required for gifts that are personalized (e.g., Books signed by the author, Gifts personally labeled).
Code of Federal Regulations
[74 FR 2396, Jan. 15, 2009]