Call It Spring Cork Wedge Shoes

This is pretty old school from brand Call It Spring a black high heel wedge sandal. The wedge is made out of cork and the front design feels like cotton. There is a string where you can tie it as tight as possible into a knot. The shoe bottom is kind of dirty which I try to clean but see no results. I am sure there are ways of cleaning which I do not know. The condition is used.