Well, 14Kt is actually an alloy made for durability on worn objects, I would not hesitate to wear a 14kt gold item myself. Generally 14kt is gold alloyed with silver, which is very tough, although it's difficult to know EXACTLY what the alloying metal(s) are / were, it's not really relevant since just about everything wears better than pure gold. It would matter if you were selling or assaying the item for it's precious metal content.
18kt is considered the purest gold alloy for wearing, 24kt is really display case material only. If this guy was actually in the gold mining business, he presumably had access to higher content gold if he wanted. Just the fact that it's 14kt to me means it was intended to be worn.
I have friends in the Gold mining business and also know two custom Goldsmiths and one of their employees very well. They routinely collect old rings, necklaces, etc and melt them down and re-cast them into new custom-made investment cast rings for customers. Usually they would add enough new gold to get the alloy up to 18kt or so.
But a belt buckle is not a ring, so I would probably go with more silver and less gold there due to the wear it's going to see, so 14kt sounds about perfect to me.