Documenting the condition of the coin: Before sending the coin, take good quality photographs of all sides of the coin and accompany them with a detailed description (including serial number, if available). This will help prove that the coin was in working condition and has not been tampered with.

Using an escrow service: An escrow service can be a great option to protect both parties. This is a third party that holds the funds until the buyer receives the item, and only transfers the funds to the seller after confirmation of receipt. Popular platforms like LocalBitcoins have built-in escrow services that you can utilize.

Shipping documents and insurance: Be sure to use trackable shipping and insurance for the full value of the coin to protect yourself from loss or damage. This will also help you prove that the package was delivered if there are questions about shipping.

Verify Buyer Feedback: Before finalizing the transaction, make sure the buyer has positive feedback and reputation on the platform where you are conducting the transaction.

Using contracts or agreements: Signing a contract with the buyer or agreeing the terms of the transaction in writing can be an additional protection. Make sure all terms of the transaction are clearly stated, including responsibility for delivery and potential claims.

By following these guidelines, you can minimize risks and ensure a safe transaction.