Assertion: key | /r/CapableOf | use six levers
Facets:
value: by 1847
type: TEMPORAL
Source sentences:
text: Chubb made various improvements to his lock: his 1824 improved design didn't require a special regulator key to reset the lock; by 1847 his keys used six levers rather than four; and he later introduced a disc that allowed the key to pass but narrowed the field of view, hiding the levers from anybody attempting to pick the lock.