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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1. •Brand: Shimano
   

2. •My category: Shimano - from Skylark to world domination, Shimano - Positron  indexing insanity
   

3. •Country: Japan
   

4. •Date of introduction: 1967
   

5. •Date of this example: unknown (no two letter date code, ‘3.3.3.’ marking on pulleys)
   

6. •Model no: unknown
   

7. •Weight: 353g including hanger plate but excluding drop-out bolt
   

8. •Maximum cog: 28 teeth
   

9. •Total capacity: 28 teeth
   

10. •Pulley centre to centre: 54mm
    

11. •Index compatibility: friction
    

12. •Chain width: 3/32”
    

13. •Logic: operated by two cables with no ‘normal’ position
    

14. •Pivots: two sprung pivots
    

15. •Material: steel
    

0185/F