Not sure. Goodle says "pd" could mean the sterling (indicated by 925) is plated with palladium.
Thank you for looking. I saw palladium too but that mark has never been in a heart that could find. I also found Premier Designs, but I couldn't find anything showing their name in a heart.
@Slnrhiannon I remember when that line was sold on QVC. I'm so sorry though that I can't remember the name of the line (I think the name of the line was an older man's who was the designer but not sure about that). All the ones I remember had enamel on them (like the one in the photo) and diamonique and he did a lot of stack rings (not sure if the one in the photo is a stack or not). This QVC line definitely had a name -- I hope I remember it. It wasn't on for very long though, it was kind of pricey. All the rings looked very well made and high-end.