For those of us who can only read English, there is a superb book on the subject of Maozhang:- Chairman Mao Badges - Symbols and Slogans of the Cultural Revolution by Helen Wang (The British Museum Press 2008) contains a detailed catalogue of 346 Maozhang in the British Museum's collection, together with related material such as lists of slogans, revolutionary song lyrics, radio programmes and other Cultural Revolution media.
Two features that make this book invaluable to the collector are that inscriptions, slogans, and many other key words and phrases are rendered in English, pinyin and simplified Chinese characters, and that both the obverse and reverse of all the Maozhang are illustrated at actual size and in colour.
My own copy is by now rather battered. Fortunately for us all the book is available free-of-charge online at:
Additions to the British Museum collection after 2008 can be found on the BM website Collections Online (search for Mao badge) at:
If you want to send photos - jpg format please, and max file size of 2Mb
GIMP (freeware) is very useful for scaling images
There is a very useful list of 600+ Chinese cities, alphabetically by province and giving names in Chinese characters at:
Unless otherwise stated, all objects illustrated on this site are in the author's collection
On Twitter look for #Maobadge