This thin cord is from the aero sets of the 30's. It was blue but thinner than traditional meccano #40 at the time. The pictured hank is from my previous life and the only pic I had, Anyone have a mint hank to photo?. From my previous notes, the cord a hank 4.25" long and an overall string length of 314" or 26 feet! By far the longest meccanoi part! It is quite thin at approx. 0.5 mm. Just like the very 1st cord on the card of cord in the teens....It is very rare to find a mint hank of aero cord and if you do, treasure it!