I agree that the buckles I’ve seen are not advertising items, but there are many made as service awards. The style of belt has changed significantly over the years and that needs to be taken into consideration when deciding on the era, the buckle above looks like it is for a wider belt, which is a 70’s or newer style.
Here’s two examples that are going to Luray next month, the brass one is a Chevrolet Parts and Accessories award that was never personalized, the silver Pontiac was likely a salesman gift and has a name engraved on the back.