Potent magic allows you to get bonuses on casting rolls using casting items. The example items in the book that use more than one item are all written like "A hazel wand with strips of silver inlaid".
My query is this. Imagine you have a potent spell. Your items are silver and hazel. An obvious device to use would be a hazel wand set with silver. Once the spell is invented however, do you need to use a hazel wand set with silver, or can you use a hazel twig and a silver coin?
Essentially, once the spell is set, if you can meet the requirements (hazel, silver) for the items actually giving the bonus, does the miscellaneous form (A wand set with...) have to be followed.
Another example. A spell that creates a great deluge of blood. The item of the potent spell is a chalice set with a ruby (+3 blood) and a bloodstone (+4 blood). If the magus lost his chalice but had a pair of rings, one set with a ruby and one set with a bloodstone, could he still cast that same spell?