To be pocket size is not a natural attribute of a scale. But when you think about what is being weighted nowadays, you get the idea. From lightweight gemstones to heavy machinery - scales are able to detect the weight of everything within the bounds of possibility.
When it comes to weighing small material precisely, there is no way leading around a pocket size scale. The models, we have these days, were originally invented by the company Tanita from japan. No matter what has to be weighted swiftly - the operational readiness and functionality of pocket scales is unmatched in this segment.
A person, who might use a pocket scale, could be for example a gourmet, who is visiting an organic-food salesman for buying truffles, caviar or other exotic food. The price of these yummy products can be horrible and heartless. This is why the gourmet always has a pocket scale in his jacket. I'm not saying the salesman is trying to pull a fast one on the groumet, but: "checking is better than shooting one's wad.", like the groumet uses to say in these situations.