Bob,
According to my photo collection, the first GN boxcars with 3M Company Scotchlight delineators (the dots or rectangles along the sill) was the 10900-11375 series built by the GN at its St. Cloud Shops in early 1948. The delineators on this series were small circular dots. Later, the GN changed to larger circles, before finally settling on the 5"x8" rectangular delineators later in the 1950s.
However, this was not the first use of Scotchlight on GN boxcars. Scotchlight was used for the "See America First - Glacier National Park" slogan in the herald, and possibly the road name as well, on plywood boxcars in the 10500-10899 series and 38700-38799 series, built in 1947, and before that on express boxcar 2500, (one of the first, if not the first, of the postwar experimental aluminum cars) and perhaps the 2501-2524 series plywood express boxcars built in 1945. I believe 2500 was the first car to get the Scotchlight treatment, but there is uncertainty as to when and what color. 2500 was built in November 1944, but was apparently repainted/relettered sometime in 1945.
Can any of the other GN fans on the list add to this or correct me?
I'm also not sure this was the first use of reflective lettering or delineators on boxcars. I know the ACL favored Prismo, which were reflective glass beads applied to wet paint, much like road markings are done today. I don't know when the practice started, though.
Regards,
Bob Heninger
Minot, ND