An 18 Size Keystone

The Keystone watch company existed for just 5 years, 1886 to 1981.  This is an example of there "dust proof" 18 size movement.  It features a full plate, a heavy duty dust band covering the outside edge, and a unique cover over the balance wheel with as acrylic window.

Things are so tight in this movement that the pallet arbor has to have a little notch so the lower pivot of the balance clears during assembly.  Without that cutout, it wouldn't be possible to get the balance installed.

Here's a detail of the two part adjustment system of the regulator.

 

The regulator features two levels of adjustment.  The part with the regulator pins moves are is usual, but that entire part rides on another piece, and so can also be micro-adjusted. This watch is missing a tensioning spring on the lower regulator platform, but it's still functional.

Here was see the cover over the balance wheel.  Once the dust band is installed around the outside edge, this movement is about as sealed up as was possible in its day.

This image shows the lever setting mechanism.




Overall this is a great watch, now running well and keeping good time!