The statute in force during the period worked, not when paid, governs back-pay classification.

Evidence

During the period for which “back pay” was awarded respondent the federal old age benefits were governed by Title II of the Social Security at of 1935. 49 Stat. 622. As Title II of the Social Security Act Amendants of 1939 became effective January 1, 1940 (53 Stat. 1362), the actual payment of the “back vages” occurred thereafter. In our view the governing provisions which determine whether this “back pay” is wages are those of the earlier enactment. — Henry M. Hart, Jr. and Albert M. Sacks, The Legal Process, 2652