This one’s for all you detectives. There are some fairly clear things: it’s a Chinese stamp, the internet advises me that it dates to roughly 1950-1952 and it features two important design elements. First we have the hammer and sickle, well recognised as the symbol for communism. And then we have the number 1.
My lack of translating skills and a dearth of easy-to-find internet explanations leave me in the realm of speculation. A good guess would be that it’s from 1950 and that it celebrates the first anniversary of the founding of the (Communist) People’s Republic of China in October 1949. Another related option is that it marks 1 October, the date of said founding and China’s National Day.
For the history of the People’s Republic of China, see the first link.
For the history of China’s postal service and stamps, see the second link.
And for a history of the hammer and sickle, see the third. The hammer and sickle together signify the unity of industrial and agricultural workers. They were used as a symbol in Chile and Ireland, before gaining their association with Communism in the Soviet Union. The Soviet version was designed for a competition run by Lenin and Lunacharsky, which was won by a designer called Yevgeny Ivanovich Kamzolkin. I don’t know why but it makes me chuckle to think of Lenin running a competition…