The box lid of my example of this set has seen better days, though I've done what I could to improve it a bit. However, while cleaning up the sides, the inside flaps that hold the side corners together came loose to reveal a couple of details I'd otherwise never have noticed.
One flap revealed the printers' trademark, stating the box was produced for "Strength & Character" by the Standard Folding Cartons company from Jackson Heights, NY.* The number beneath it could be their job code for producing this batch of box lids, or just a reference number for this particular item.
A second inner flap revealed a symbol which indicates a production date of July 1969, with a tick across the 7 to specify the month production took place. Which is very nice to know, as it helps to narrow down when GA toys became available in 1969.
Box size
Length
Width
Height
50 cm
51 cm
4.7 cm
19 11/16 in
20 1/16 in
1 13/16 in
*: The company still exists, and has a brief history page on its website (opens in new window).