14 CFR § 1214.602 - Policy.

Premise. Mementos are welcome aboard NASA missions. However, they are flown as a courtesy—not as an entitlement. All mementos must be approved by the Associate Administrator for Human Exploration and Operations and are stowed only in an Official Flight Kit (OFK) or Personal Preference Kit (PPK).

(a) Economic gain. Items carried in an OFK or a PPK will not be sold, transferred for sale, used or transferred for personal gain, or used or transferred for any commercial or fund-raising purpose. Items such as philatelic materials and coins that, by their nature, lend themselves to exploitation by the recipients, or create problems with respect to good taste; or that are large, bulky, or heavy items will not be approved for flight.

(b) [Reserved]