For any kind of tangible object that has been designed and created with the intention of being sold exclusively by the creators, the first step is to apply for the following two types of patterns:
1. The utility patent, which is described by the US Pattern and Trademark Office (USPTO) as one issued
for the invention of a new and useful process, machine, manufacture, or composition of matter, or a new and useful improvement thereof, it generally permits its owner to exclude others from making, using, or selling the invention for a period of up to twenty years from the date of patent application filing ++, subject to the payment of maintenance fees.
Therefore, this is the patent you need to apply for first to secure the design from being copied or from being taken from you.
The second patent to apply for is
2. Design patent, which is described by the USPTO as one that is issued for
new, original, and ornamental design for an article of manufacture, it permits its owner to exclude others from making, using, or selling the design for a period of fourteen years from the date of patent grant.
Now, you may ONLY use the design pattern, but there is a also a mechanism that has been applied to the belt buckle's design. Therefore, it is best to be safe and go with both applications so that the mechanism and the design are equally protected. The design patent does not carry with it maintenance fees, which is a benefit. All that you need aside from the applications is the application fee for each, and the complete description of the belt buckle.