To me, it looks like an ad for something like milk powder.
When you say covered box, is it covered on top of the print, or as part of the print?
Any writing to a lower front corner, might be faint.
Have you tried looking up the info on the rear label. Might give you a date they started/went out of business and that might help you pin down a date range.
If you send a photo into one of the better art auction houses they should be able to give you a guide.
Hope this helps a bit.
