21 Pa. Stat. § 283.3
Whenever, prior to December 31, 1965, any property was sold by a county treasurer for the purpose of securing the payment of delinquent taxes which were assessed and levied against such property, and no proof of service was filed or in lieu of personal service the property was not properly posted or if it was properly posted the certificate of posting was not filed or as if the proof of service had been filed, or if no proof of service was filed, if, in all other respects the law relating to the holding of such sale was fully complied with, all such sales and county treasurer's deeds are hereby ratified, confirmed and validated and the title to any such property purchased by any person or by the county commissioners of the county is hereby declared to be as valid as if the proof of service had been filed or as if the property had been properly posted or the certificate of posting had been properly filed.
21 P.S. § 283.3