I've seen this half on now and half later across a few recipes.
The recipe I used is from Home Production of Quality Meats and Sausages by Stanley Marianski so it should be a reliable recipe.
Recipe as follows (note that I scaled the recipe for my meat weight).
1000g - 2.2lb Coppa
30g - 2 3/4 tsp salt
6g - 1 tsp cure #2
25g - 2 tbs sugar
Then there's a bunch of spices which I've omitted.
Method is: mix the cure, rub half on the meat and place in fridge in zip lock bag for 7 days. After 7 days, rub remaining curing on and keep in fridge for another 10 days.
Remove, rinse, dry for 3 hrs in fridge, add spices, stuff into bung, hang @ 14c / 55f @ 70% humidity.