Box of 36 1960s Plastic Rulers - 12"/30cm Green, Red and Blue

Unused 1960s/70s Box of 36 Plastic Rulers
Opaque plastic, 12 each of red and blue, and 12 green see through plastic.
They are 12" / 30.5cm long - inches on one side, cm on the other
Made in Hong Kong stamped on the ends.
Could actually be used for all sorts of things - not just measuring !