Reinstatement of a lapsed.
Section 23
SEC. 23. Reinstatement of a lapsed.—Within two years from the date on which the first unpaid annual fee was due, a patent which has lapsed for nonpayment of any fee may be reinstated upon payment of all annual fees then due and surcharge for reinstatement, and upon proof satisfactory to the Director that such nonpayment was due to fraud, accident, mistake or excusable negligence: Provided, however, That such reinstatement shall not be prejudice the rights acquired by a third person while the patent was not in force.