See also ULCA 29 Administrative History.
The concept of the thank offering was not a new one when the Women's Missionary Society (WMS) of the United Lutheran Church in America (ULCA) formed in 1918. Each of the merging societies from the General Council, General Synod, and United Synod of the South had instituted a thank offering as part of their fund-raising efforts. Thank Offering boxes, specially designated mite boxes, were used to collect the monies received.
From the description of Thank Offering Boxes 1924-1957. (Evangelical Lutheran Church in America Library). WorldCat record id: 49309030