Addressee refused to accept mail or pay postage charges on it."
I think it says that the package will be returned to you, because it's refused mail.http://pe.usps.com/Archive/PDF/DMMArchive0810/F010.pdf
is old but I think that the Sig Conf and insurance are still Special Handling and read the bold parts, lol:
Mail with special services is treated according to the charts for each class of mail
in 5.0, except that:
a. Undeliverable-as-addressed certified mail is treated as First-Class Mail.
b. All insured First-Class Mail is forwarded and returned at no additional cost. All insured Standard Mail and Package Services is forwarded or returned.
c. Parcels with special handling that are undeliverable as originally addressed and forwarded to the addressee continue to receive special handling service
without an additional special handling fee.
d. Undeliverable-as-addressed return receipt for merchandise mail receives the treatment appropriate for the class of mail of the host piece.
e. All registered mail items are treated as registered while they are being
forwarded or returned.
So, I believe the same applies to insured packages returned to sender: On the return, they're treated as the same class sent. But I can't find the exact policy that applies here.
Ask / search at the ebay forums. Probably somebody has dealt w/ jewelry mailed the exact same way and will know the answer.