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.
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).