A free appraisal is worth every penny you pay for it.
I'd suggest taking the earrings, and their packaging to a Tiffany dealer. If there isn't one in your community, try Birks or a similar high end jewelry store.
The kind that have to buzz you in and are in a 'nice' neighbourhood.
Then just ask if the counterperson thinks they are the real thing.
There doesn't appear to be much silver in them by weight, so most of the value, as you have guessed is in the name. On the other hand, I can't see it being worthwhile to pay for a formal written appraisal.