When Shimano launched the Shimano Dura-Ace (7970 SS), it seemed to me to be impossibly glossy, glamorous and exotic. Britain was just entering the second 'dip' of a 'double-dip' recession. Well-healed Tory politicians were bleating on about the death of conspicuous consumption and the need for a new 'austerity'. Almost-as-well-healed Labour politicians were writhing in mock agony, pretending to share the, very real, pain of the newly impoverished. And amidst this theatrical orgy of doom and gloom, Shimano was releasing by far the most technologically advanced and extravagantly expensive groupset in its long history. It was as if it had travelled from Mars.

But now, when I look at this derailleur, it seems quite understated, almost humble. The dark matt finishes, the self-effacingly modest logo and the form, that largely follows function with few extravagant flourishes, are all almost endearing. In particular, the Dura-Ace (7970 SS) looks rather petite and svelte, lacking the gross, oversized rear-end of the later cheaper, commoner Shimano Ultegra (6770 SS). Perhaps the decade of cycling excess that has passed since its launch has dulled my senses.

Make no mistake, the Shimano Dura-Ace (7970 SS) was an epoch-defining derailleur. In much the same way that, 25 years previously, the Shimano Dura-Ace (7400) had marked the point at which Shimano had stopped playing at indexing, and was ready to revolutionise mechanical shifting for a generation. So the Shimano Dura-Ace (7970 SS) signposted that electronic shifting was no longer the crazy uncle locked in Shimano's attic, but had moved to the front and centre of the stage. Di2 was ready to dominate the next 25 years.

As an aside, I note that, on the evidence of its pulley wheels and pulley cage, this example has covered a fair few miles. But it has retained its looks, and as far as I can tell from a very brief check, it functions fine.

• Derailleur brands: Shimano
• Categories: Shimano - the Dura-Ace story
• Themes: Electric Avenue
• Country: Japan
• Date of introduction: 2009 for the 2010 model year
• Date of this example: 2012 (two letter date code KC)
• Model no.: 7970 SS
• Weight: 226g
• Maximum cog: 27 teeth
• Total capacity: 32 teeth
• Pulley centre to centre: 56mm
• Index compatibility: 10 speed
• Chain width: 3/32”
• Logic: top normal
• B pivot: sprung
• P pivot: sprung
• Materials: carbon p-knuckle and pulley cage plates, aluminium b-knuckle and parallelogram plates