Solution
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Priority : It is usually a fast type of shipping (by air for international). It sometimes can enable real time monitoring of the delivery if the postal service offers a tracking number.

Used method by the seller for this type of shipping :

Economy

Registered : It is usually a fast and secure type of shipping providing legal evidence of delivery and sometimes an insurance for the seller in case of loss or breakage.

Used method by the seller for this type of shipping :

Priority Air Mail