I ship via USPS but they don’t offer insurance. Your customer will
need to be responsible for any customs, duties, etc.
DHL is who I have used for shipping expensive art work (not jewelry -
paintings and such).
Shipped some medicine to Greece via UPS this summer and it was a
disaster :(The local office didn’t put the correct forms on the
parcel, it got held up in Customs in Greece, nearly missed arriving
by when it was needed, and cost a small fortune in added fees because
of the incorrect forms. So I sure won’t use them again for
international shipments of anything