1983 was a tumultuous year for Campagnolo. On the downside, Tullio Campagnolo sadly died at the age of 81 on the 3rd of February. On the upside, later that year the company celebrated its 50th anniversary.
To celebrate its 50th Anniversary and to honour the memory of Tullio, the company released a special, limited edition, '50th Anniversary' groupset. I believe that 15,000 of these groupsets were manufactured, with each accompanied by an individually numbered card. The rear derailleur in this groupset was a Campagnolo Super Record of the time, enhanced with a '50' logo, real gold detailing and an embossed signature of Tullio Campagnolo.
Groupset number 2 was presented to Pope John Paul II at a ceremony in the Vatican. Groupset number 1 was kept by Campagnolo. Inevitably, sharp tongued wags quipped that these numbers were entirely appropriate because most cyclists considered that Tullio was one step closer to God than His Holiness.
By way of an aside, I believe that Pope John Paul II was something of a cyclist, with the museum dedicated to him in his native Poland displaying a number of his bicycles. It was also rumoured that, even as an elderly Pope, he liked to ride a flat-bar Colnago around the grounds of one of his palaces.
I am particularly pleased that this example of a Campagnolo 50th Anniversary derailleur shows real signs of active use. There are chain wear marks on the pulley cage plates and a scuff on the allen bolt at the b-knuckle. You had to be wealthy to afford one of these groupsets, but you had to be at ease with your wealth to put some miles on a bike fitted with one.
It's the ideal derailleur for cycling through the eye of a needle.