It it the Chinese railway insignia. You can also see it in this painting on the man’s teacup.
On the left top back corner wall the blue-grey characters, 批林批孔专栏 mean, “Billboard for Criticizing Lin Biao and Confucius.” On the right top corner is an old style loud speaker box with a red five-star on it. This was used for making public announcements. You…
The characters 为人名服务 “Service to the People,” written by Lin Biao. Image of the back of the badge has the characters 包头, the place of origin “Baotou.”
The name comes from a poem by Mao Zedong called “Three Short Poems” 1934 – 1935. 山 Mountains! 快马加鞭未下鞍。I whip my swift horse, glued to my saddle. 惊回首，I turn my head startled, 离天三尺三。The sky is three foot three above me!