The story of the Campagnolo Gran Sport begins immediately after the Second World War. It was a time when cycle racing was dominated by two Italians - Gino Bartali and Fausto Coppi.

Gino Bartali, a conservative man who saw himself as a skilled craftsman, loved the intricasies and complexities of Tullio Campagnolo's Heath Robinson rod-operated gear changers like the infamous Campagnolo Corsa. He used one to win the 1948 Tour de France.

Fausto Coppi, however, revelled in modernity, progress and technology - and despised Tullio's ornate contraptions. In 1949 Fausto Coppi defected from Campagnolo to Simplex, and horror of horrors, won the Tour de France. An Italian demi-god had triumphed using French equipment. Tullio Campagnolo was humiliated and mortified.

But the shock was exactly what was needed to get the, ever-cautious, Tullio off his backside and spur him to produce, in 1951, his signature Campagnolo Gran Sport derailleur. It, famously, adopted a parallelogram mechanism, and its strength and accuracy defined the way that derailleurs operate up to this very day.

For the 1952 season, Fausto Coppi returned to the Campagnolo fold and won the Tour de France by a trifling 28 minutes. For the next 50 years Campagnolo was the unchallengeable king of the peleton, although perhaps not always the unchallengeable king of consumer markets.

There are people who know an almost unimaginable amount about the many and various variants of the Campagnolo Gran Sport. Unfortunately I am not one of them. Here is an ignoramus' list of possible variants (with approximate dates):

• 1949 - The twin cable prototype
• Early 1951 - The first single cable models with large main bolt, cable adjuster, drilled pulleys, a symmetrical outer pulley cage plate, 3.5mm deep p-spring cover cup, cable clamp very near the top of the outer paralleogram plate and an angle adjuster on the b-pivot.
• Later 1951 - As for early 1951, but there is no angle adjuster on the b-pivot.
• 1952 - As for later 1951, but with a more normal cable clamp placing and an extravagant extension loop at the guide pulley end of the outer pulley cage plate. These models are sometimes called Gran Sport Extra.
• Early 1953 - The first of the classic Gran Sports. Small hollow main bolts, cable adjuster, solid pulleys, symmetrical outer pulley cage plate and a p-spring cover cup that is 3.5mm deep.
• Later 1953 - As for early 1953, but main bolts are no-longer hollow and the p-spring cover cup is now 5mm deep.
• 1956 - As for later 1953, but the p-spring cover cup is now 8mm deep.
• 1960 - As for 1956, but the cable adjuster is eliminated.
• 1963 - As for 1960, but the p-spring cover cup is now 10mm deep.

Readers should note that these are not settled facts - many experts seem to disagree about the exact dates etc.. There may also be very small variations within each of these generations - for example early models with drilled pulley wheels may have different numbers of holes drilled in their pulleys. But at some point I just have to give up!

And this is not all, there is also the question of the Campagnolo part numbers:

• An un-numbered catalogue, from 1951, shows a 'later 1951' Gran Sport - but gives no part number for it.
• Catalogue No 12, from 1953, shows a classic 'later 1953' Gran Sport and gives a part number 1012/1.
• Catalogue No 13, from 1954, shows exactly the same drawing and part number as in Catalogue No 12.
• Catalogue No 14, from 1958, possibly shows a 1956 Gran Sport, and gives a part number 1012/4.

Many experts regularly refer to derailleurs with part numbers 1012/2 or 1012/3. But it is not clear to me what the number after the '/' means. If it refers to some kind of generation of the variants, I am not clear how this number maps onto the various variants listed above.

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This particular example of a Campagnolo Gran Sport has:

• no cable adjuster
• a 10mm deep p-spring cover cup between the pulley cage and the p-knuckle casting.

I think this indicates that it dates from around 1963.

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• Derailleur brands: Campagnolo
• Categories: Campagnolo - the good stuff
• Country: Italy
• Date of introduction: 1963
• Date of this example: unknown
• Model no.: 1012
• Weight: 304g
• Maximum cog: 26 teeth (stamped on the inner parallelogram plate). Note that various versions of Sutherlands quote various, often much larger, figures.
• Total capacity: 18 teeth? (this is from bike shop folklore only). Again note that various versions of Sutherlands quote various, often much larger, figures.
• Pulley centre to centre: 43mm
• Index compatibility: friction
• Chain width: 3/32
• Logic: top normal
• B pivot: unsprung
• P pivot: sprung
• Materials: bronze knuckles, steel parallelogram plates, steel pulley cage plates and steel pulleys