Are the belt buckle back parts also silver, or something else like nickle? I know your buckle is solid silver, but thought that the back parts might need to be something less bendy than silver?
On most Native American made buckles:
The bar hinge mechanism is nickel silver.
The bar is nickel silver.
The prong is nickel silver.
You can read more here
The entire buckle plate is sterling silver and just to clarify, that is sterling silver not 100% pure silver. Read about nickel silver and sterling silver here All Silver is Not Created Equal
As you say, the working portion of the buckle needs to be something “less bendy” than silver- especially if the belt is worn tight as the prong could straighten out or the bar could bend if made from a soft metal.
Good question ! We wear buckles all the time and this is the normal way they are made and work fine for many many years.