This is not uncommon, especially with early San Francisco Morgans. Every new die was polished to a really fine finish, and it imparted that reflectivity to the first few (maybe as many as 100?) coins it struck. If it meets the "legal" definitions of Prooflike or Deep Mirror Prooflike, it's an added-value feature. Either way, there's no look like a big Morgan cartwheel with reflective fields.
