Beginning in 1948 with No. 397-49 that is dated 12/48. After this sheet the number was altered to No. 397-64. The first issue of this sheet is not dated. Subsequent issues are dated 2/49 (some issued with DARK BLUE ink on LIGHT BLUE paper), 11/49, 8-52, 4-53, and 5-55. With the exception of the printed colors noted above and below, all of these sheets are issued with BLACK ink on WHITE pager.
Some of the sheets dated 8-52 and 4-53 are found with BLUE ink on WHITE paper.
Early metal bases would be painted GRAY, while later issues have a hammered tone finish. The earliest generators would have various colored plastic that was painted YELLOW, while the later more common versions would be painted BLUE. Also, the coal bin changed from being RED painted BLACK plastic, to solid RED (sometimes with a hi-gloss finish) plastic.