National Workers Federation
Nisan (month of Hebrew calendar), (Jewish year) 5694 (1933-34) to Nisan, 5709 (1958-59)
There are two major labor federations in Israel and both of them have the Hebrew term "histadrut" in their names.
1) The General Histadrut of Workers in Eretz Israel which emerged from the labor movement in 1920. This poster is not from that group.
2) The National Histadrut of Workers (National Workers Federation) which originated from the revisionist movement 1934. This is the group that published this poster.