Wash-leather
A similar entry appears in the Wheel of Time Companion confirming the information available in the main story arc.
General
Washleather is a material used for (as far as we know) making of bags and coin purses. Usually the bags or purses are of a size big enough to fit into a coat pocket.
References
Moiraine hands a washleather purse to Master Gill to cover the expenses for their needs when they leave Caemlyn. (TEotW, Ch. 43)
Gaebril gives Mat a purse full of coins in exchange of bringing Elayne back safely. (TDR, Ch. 46)
Nynaeve is keeping a Seal to the Dark One's prison in a washleather purse, brought from Tanchiko. (TFoH, Ch. 9)
Eagan Padros is using a washleather pouch to keep his coins. After he was killed Rochaid turned the pouch inside out to see the coins (TPoD, Ch. 22)
Mat is keeper a present for Tuon in a washleather made bag. (CoT, Ch. 28)