The coupling between two flatcars at Beacon Yard, Boston, Massachusetts, United States.
The "knuckle coupler" like the example shown was invented by Eli H. Janney who was awarded U.S. patent 138,405 in 1873 for his design. The 1893 US Railroad Safety Appliance Act in part mandated the use of automatic couplers like those invented by Janney. Couplers like these are now in use worldwide.
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