Supposedly, in the old days, Black Diamond Strings were just about the only brand you could get. I don’t have any experience with them but I’ve been told that these things were really “stiff.” I don’t have a date for this box but the price was $2.10. Maybe 60s?
Vintage guitars are fantastic but vintage strings, well, I don’t think they peaked in the 1930s or 40s. I did a quick google search and came up with this little ditty: