11MW and 13MWZ
11MW and 13MWZ are the style numbers of the two famous “Cowboy Cut” jeans marketed by Wrangler and designed by celebrity cowboy tailor Rodeo Ben.
The ‘MW’ is short for ‘Men’s Wear’ and ‘Z’ naturally stands for ‘Zipper.’ The 11MW was introduced in 1947 by Blue Bell as the flagship of the new Wrangler brand; a separate denim line under the company.
The 13MWZ was allegedly first introduced five years later, in 1952. One source claims that the numbers refer to the weight of the denim, another source states that it’s a referral to the number of times the design was changed.