72 Pa. Stat. § 3966
All provisions and amendments thereto relating to information and reports, to be furnished by the Governor and the State Treasurer to the General Assembly, contained in the act, approved the eighteenth day of April, one thousand nine hundred nineteen (Pamphlet Laws, sixty-two), under the terms of which were issued the bonds of "Series 'D' Loan of the Commonwealth of Pennsylvania," which bonds are to be redeemed or retired by, or exchanged for, the bonds issued under the provisions of this act, shall continue in full force and effect, and shall be deemed to apply to the refunding bonds issued under the provisions of this act.
All bonds issued under the authority of this act, shall be redeemed at maturity, and all interest due, from time to time, on such bonds shall be paid from the sinking fund. For the specific purpose of redeeming said bonds at maturity and paying all interest thereon, and in accordance with the information received from the Governor, the General Assembly shall appropriate biennially the moneys necessary for the payment of the interest on said bonds and the principal thereof at maturity. All moneys so appropriated shall be paid into the sinking fund by the State Treasurer, and all of such moneys not necessary to pay accruing interest, shall be invested by the Board of Finance and Revenue in such securities as are provided by law for the investment of the sinking funds of the Commonwealth.
The investments and such moneys and the accumulations thereon in the sinking fund shall be devoted to, and used exclusively for, the payment of the interest accruing on such bonds and their redemption at maturity: Provided, however, That the Board of Finance and Revenue is authorized at any time to use any of such funds for the purchase and retirement of all or any part of the bonds issued under the authority of this act. In the event that all or any part of said bonds shall be purchased by the Board of Finance and Revenue, they shall be cancelled and returned into the State Treasury as cancelled and paid bonds, and thereafter all payments of interest thereon shall cease.
72 P.S. § 3966