In the listing there are duplicates because of the confusion of the different manufacturers names. Such as those under the names of CHINA SHANGHAI and SHANGHAI (China) that may not be manufacturers at all. There are many Chinese slide rules and I expect more will be found and added to the list as time goes by. Fortunately some of my confusion in how to list these has been lessened by Liu Qinglin, a slide rule collector and dealer, who lives in Beijing. He informed me that the SIDA company was formed in the 1930's. Then later in the 1960's united into the Shang Hai factory. He says slide rules listed as China Shanghai and Shanghai China are the same maker, and that Flying Fish and Ruyi are Trademarks.. Also, where the slide rule numbers are the same the scales are the same layout. For example, the Flying Fish 1015 slide rule is the same as the RUYI, SIDA, and Shanghai (SHANG HAI) rules with the same number of 1015. I know his comment to be true for some of the names, but as I only have a few of each of the various models for a cross-check it has not been verified. Also, this information only covers one manufacturer. What is the story about the other makers such as Ding Feng, Haiou Pai, Hangzhou, Hua Fang, Jang, Xuesh and unknown others? Who are they and where were they? In April 2009 a Chinese collector, Xu Guisheng, sent me information and a listing of Chinese slide rules that was cross-checked to my list. This was very helpful. I wish to thank Pierre Vander Meulen for the many pictures he emailed to me showing details of the slide rules he collected when he worked in China (See the initials PVM at the right end of the listings for his contributions). If you know of Chinese slide rules that need to be added, or you see something on the list that needs correction, please send me the details. Pictures front and back and details of the gauge marks on the scales and cursor. Since the above note was written an article on Chinese slide rules, written by Richard Smith Hughes and myself, has been published in the JOS Vol. 14, No 2; and a listing of the Chinese rules is on the JOS PLUS web site. The listing on the JOS Plus web site (of Chinese slide rules with hyperbolic scales (Vectors)) will be updated from time-to-time by Richard and myself as new information comes in.