Improvements to an upper hook for a three-point hitch

The hook has a main body (12) with a hooking mouth (24) ending in a curved jaw (26), and a shutter (14) mounted to move in a hole of main body to close a part of mouth in a locked configuration. The shutter is made from a quenched and tempered steel surface hardened in a zone (54, 56) adapted to come into contact in the locked configuration with a coupling ball housed in the mouth.