From and after the passing of this act, it shall be lawful for the secretary of the land office to issue warrants to any person entitled thereto, within the purchase of 1768, or the previous purchases, at the rate of ten pounds per hundred acres, charging interest within the purchase of 1768, from March 1, 1770, and within the previous purchases from March 1, 1755, in cases where the applicant cannot obtain proof of the time the said land was first improved as required by the existing laws.
64 P.S. § 62