Elgin Grade 62, The Geneva Stop

Some older Elgin 18 size pocketwatches include what's called a "Geneva stop" under the mainspring barrel. Often these parts are missing, but this movement has them. Notice how two of the six leaves on the stop wheel bow outward while the other four are concave.

The turning of the mainspring arbor, either while winding or unwinding, is thus limited to four full rotations, a typical "wind" being a half-rotation of the key.

The movement is a grade 62, an 18 size, 15 jewel product, made about 1867. It's also an H. Z. Culver model.