35 Pa. Stat. § 1558
The bonds of an Authority shall be authorized by its resolution, shall be issued in one or more series, and shall bear such date or dates, mature at such time or times, and bear interest at such rate or rates, not exceeding six per centum (6%) per annum, payable semiannually, be in such denominations, be in such form, either coupon or registered, be executed in such manner, be payable in such medium of payment, at such place of places, and be subject to such terms of redemption, and carry such registration privileges as may be provided in such resolution or in any trust indenture or mortgage properly made in pursuance thereof.
The bonds of an Authority may be sold at not less than par and accrued interest. In case any of the officers of an Authority, whose signatures appear on any bonds or coupons, shall cease to be officers before the delivery of such bonds, their signatures shall nevertheless be valid and sufficient for all purposes the same as if such officers had remained in office until such delivery.
The Authority shall have the power, out of any funds available therefor, to purchase any bonds issued by it at a price not more than the par value thereof, plus accrued interest: Provided, however, That bonds payable exclusively from the revenues of a designated project or projects shall be purchased only out of any such revenues available therefrom. All bonds so purchased shall be cancelled. This paragraph shall not apply to the redemption of bonds.
Any bond reciting in substance that it has been issued by an Authority to aid in financing a housing project to accomplish the public purposes of this act, shall be conclusively deemed in any suit, action or proceeding, involving the validity or enforceability of such bond or security therefor, to have been issued for such purpose.
35 P.S. § 1558