Here is the street vendor photo someone mentioned earlier.
Last Hope, although not an exhaustive source, does document the variations of the cloth chits produced by the Chinese Aero Commission and those mass produced by the U.S and Britain. The "may guo" or "American" stamp is documented in Last Hope in two shades of purple, black and hand written. There are several variations among the cloth chits issued to the AVG.
In the preface to the book Baldwin mentions, "I do not pretend to be an expert on the history of Blood Chits and related evasion aids. I consider myself a student of that history." He also adds, "...I am considerably less knowledgeable about the theater-made souvenir patches." Several examples of leather chits are presented in the book. In a way, all of the leather chits made in India are copies of the "official" issued chits. Artisans, who did not read Chinese, just reproduced what they saw. I've seen examples where the Chinese text for "serial number" is reproduced. Often the leather chit will give an indication as to which issued cloth chit was being copied by including the same variations as the cloth chit. Once purchased an airman could personalized their chits with personal chops or have a local craftsman in China write additional text. What is or isn't on a leather chit can't always indicate it's authenticity. There was no official source for leather chits. Variations, mistakes and multiple sources add to the multitude of possibilities. The best way to authenticate a piece is to become familiar with vintage pieces having known provenance. A resource like Last Hope is invaluable if you decide to collect vintage chits. The Maguire books are also a great resource. No desire on my part to start an argument, just want to clarify why I hold my opinion.
Here are two of my fakes or as I like to call them, authentic reproductions.