Compared to the, earlier, Sun-Bow YA100, this Sun-Bow ELF400 was a masterpiece of style and function. Compared to a SunTour Honor, or indeed any other low-end SunTour or Shimano model of the time it was an ugly and poorly finished lump.

I have guessed its date as being 1979, only because it looks to be later than the 1977 Sun-Bow YA100, but not that much later.

I have not yet managed to make even a decent guess at what 'ELF' might stand for. I am assuming that it is an acronym and not a reference to one of Santa's little helpers.

• Derailleur brands: Sun-Bow, see also SY
• Country: Japan
• Date of introduction: 1979?
• Date of this example: unknown
• Model no.: ELF400
• Weight: 386g including hanger plate, and drop-out bolt
• Maximum cog: 28 teeth?
• Total capacity: 28 teeth?
• Pulley centre to centre: 55mm
• Index compatibility: friction
• Chain width: 3/32”
• Logic: top normal
• B pivot: unsprung
• P pivot: sprung
• Materials: steel