A chrome vintage style Telecaster cup jack with a retainer clip. The retainer clip design of cup jacks is vintage accurate, but has been quickly superseded by the cup jack with screws (here). It's almost always preferable to use the screw version, as there's some durability issues that can come with the retainer type. But, where vintage accuracy is necessary - here's the style that Leo Fender designed all those years ago.
These install into a guitar by the retainer clip biting into the sides of the jack cavity - it's installed bent and then widened in the cavity so that it is secure. The jack then threads through the hole in the middle and the cup is then placed over it. Threading the jack nut onto the jack with the cup and retainer clip behind it secures all three components together.
Dimensions:
Cup diameter: 26mm
Cup hole diameter: 10mm
Cup depth: 10mm
Clip length (bent): 20mm
Clip length (maximum, flattened): approximately 23mm
Clip width: 12mm
Clip hole diameter: 10mm