This is a Taiwanese copy of a mid 1970’s Shimano Skylark - right down to the large squarish typeface of the logo on the outer parallelogram plate.
It omits so many of Shimano’s later, cost saving, features that I think it is a fairly early derailleur for Taiwan. Notably, it has the swivelling adjustable outer cable stop, the adjuster screws with springs to stop them loosening (rather than the later plastic piece) and the cable clamp on the front knuckle (not on the outer parallelogram plate).
The pulley wheels on this example are branded as ‘SunRace’, so I would guess that it is made by SunRace.
- Derailleur brands: Lepper, manufactured by SunRace?
- Country: Netherlands, manufactured in Taiwan
- Date of introduction: 1980?
- Date of this example: unknown
- Model no.: unknown
- Weight: 285g including hanger plate but excluding drop-out bolt
- Maximum cog: 28 teeth
- Total capacity: 28 teeth
- Pulley centre to centre: 53mm
- Index compatibility: friction
- Chain width: 3/32”
- Logic: top normal
- B pivot: sprung
- P pivot: sprung
- Materials: steel