Laces made of raw-hide leather, natural color. Rawhide leather sustains repeated soaking and drying better than usual shoe leather. Therefore, these laces are better for heavy-duty use. In addition, they are "old-looking".
Thickness 3 mm, width 4-5 mm, Price for 1 long strip (1,75 m or around 69 in). If you one strip is enough for your pair of shoes, take one; if not, take more.
Textile laces were also current during the war, however, leather laces didn't rot and not torn from getting wet. The disadvantage of the leather laces was that they are quite difficult to untie when wet. However, rawhide, well-impregnated with fat, smoothed this deficiency, and was the best option.