
A closer look:

These are the smaller cords on the card. The left one is brown, the right one black.
The upper scale is 1/64 of an inch per division, the lower scale is 1 mm per division where the cord is (0.5mm to the left of the cords.)
The cords are about 1 mm (0.039 inch) in diameter or 1.9 inches in 1:48 scale.