72 Pa. Stat. § 3648
The commissioners of the sinking fund are hereby authorized and required, from time to time, with the surplus moneys on hand, to purchase for redemption such amounts of the state loans and certificates of indebtedness as the condition of the sinking fund will justify, at such rates as may be to the interest of the commonwealth, purchasing those loans which first fall due, as far as practicable; such evidence of indebtedness, when redeemed, shall be cancelled and destroyed by said commissioners, after a detailed record of the same shall have been entered on the books of the auditor general; and a report of all transactions under this section shall hereafter be included in the annual report of the commissioners to the legislature.
72 P.S. § 3648