• 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.