Here the fork end, that faces the balance wheel, is on a line perpendicular to
the tangent line of the escape wheel. The pallet stones engage with the escape
wheel along the tangent line.
This is the classic Swiss style escapement that is still used on almost all
mechanical watches today.
The American watch industry transitioned to this design from the older,
English style pallet configuration that placed the fork at the end of the
tangential line, not perpendicular to it. Older Elgins (and Walthams and
others) have this older style.
The different is that the leverage between the pallet end and the fork end on
the Swiss style creates a higher velocity at the fork end thus tending to more
easily move right through slight errors in the escapement due to motion of the
watch, or imperfections in the arms of the escape. The "amplified" motion of
the fork end also assures good escapement functionality with minimal locking
face contact, thus reducing wasted lift and friction. The Swiss design is more
stable and less error prone.
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