Hey, thanks for the reply! I actually wasn't too interested in how much it is worth (unless it is significant, of course). The reason for that is tied to the reason the fill seems low. We believe current ullage is due to the previous owner's storage. My father has since "plugged the leak" with wax, or something of that nature, but the missing wine is gone for good.
How old were you thinking this bottle is, though? How can people usually tell when there is no indication on the label? That would actually be my real question here I think.