What is a primary characteristic of the 3813-P insurance form?

The 3813-P insurance form is specifically designed to provide coverage for items with a declared value over $500. This form is essential for shipping valuable items through the USPS, as it allows customers to insure their packages against loss or damage. By utilizing this form, customers can protect their high-value shipments and ensure they receive compensation in the event of any issues during transit.

The other options do not accurately describe the primary purpose of the 3813-P form, as it is not intended for items valued under $500, is not used for certified mail, and is not limited to international shipments. The emphasis on higher-value items makes the 3813-P form an important tool for anyone shipping valuable goods.