I think that the Lark name was first used on this derailleur - the 1967 Shimano Lark-W. The W designation indicates that the derailleur has no spring in the parallelogram and is controlled by two cables, pulling in opposite directions, worked by a twist-grip. Like the Shimano Archery-W and unlike later Shimano Lark-W’s, the cable nipples in this model are at the twist grip, and the clamp bolts are on the derailleur.

Aside from the W system, this is a very similar derailleur to the 1967 Shimano Skylark, except that the adjustment screws have been moved to the other side of the outer parallelogram plate - to make way for the twin cables.

This is an early example with aluminium (?) nameplate and the screw stop for the pulley cage.

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• Derailleur brands: Shimano
• Categories: Shimano - from Skylark to world domination, Shimano - Positron indexing insanity
• Country: Japan
• Date of introduction: 1967
• Date of this example: unknown (no two letter date code, ‘3.3.3.’ marking on pulleys)
• Model no.: unknown
• Weight: 353g including hanger plate but excluding drop-out bolt
• Maximum cog: 28 teeth
• Total capacity: 28 teeth
• Pulley centre to centre: 54mm
• Index compatibility: friction
• Chain width: 3/32”
• Logic: operated by two cables with no ‘normal’ position
• B pivot: sprung
• P pivot: sprung
• Materials: steel