It turned out to be a club station called "YinZhou Middle School Amateur Radio Club Station" which is located just south of Shanghai.
It is interesting to consider the age of the operators as one can see from the picture. More pictures and some information can be found on their QRZ.com website. With this many young people entering ham radio in China, maybe we will see more stations there in the future. The number of stations is unreasonably low compared to the enormous population of China.
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The image shows "GM5X GM5X Test". The long path signal seems to fade in and out as there is much less of it in the last part, the word "test", than in the second "GM5X".