Here we go! I don't have much on the very genesis of the string or cord used in Frank's first sets in the very early years. He is said to have included a Knot, ball and hank of cord in a "natural" color..what ever that is! I have never seen a picture of one in this color. Anyone got one? The earliest surviving balls and knots are very rare indeed. This green one comes from Malcolm Hanson. Unknown how long or thick it is? These don't turn up very often as most of the early sets did not survive. It is speculated that the ball or knot of cord could have also come in blue( I think I have seen a pic somewhere?) and black as well as the so called natural. I would love to see pics of any of this very early stuff....Until then, I will leave it to you early experts to fill this in...