58 Pa. Code § 165.55
If any registered stockholder provided for under this subchapter is not, or is not to be, the sole beneficial owner of such stock the registered stockholder shall annex to the affidavit required under this subchapter, and expressly state in said affidavit to be deemed a part thereof, a true and complete copy of all terms of the agreement pursuant to which the stock is to be so held by the registered stockholder, including a detailed statement of the interest therein of each person who is to have any interest in such stock. No person may hold stock as a registered stockholder for the benefit of any other person unless a duly executed agreement in writing exists setting forth all of the respective rights of the registered stockholder and the beneficial owner or owners, as well as all of the terms of the agreement between the registered stockholder and such beneficial owner or owners, and the same is attached to said affidavit.
58 Pa. Code § 165.55
This section cited in 58 Pa. Code § 165.13 (relating to filing of information concerning stock transfers); and 58 Pa. Code § 165.58 (relating to change of status of affiants who are beneficial owners).