Which of the following is not considered a weigh master?

A common carrier issuing way bills is not considered a weigh master because they typically do not have the responsibilities or the qualifications required to weigh goods for the purpose of certification or official measurement. In the context of weight verification, a weigh master is usually an individual or business authorized to weigh commodities and provide legal measurements that can be used in transactions.

The other options represent entities that involve weighing goods as part of their business operations. For instance, sand, rock, and gravel companies that sell by weight need to have accurate weight measurements to ensure fair trading and meet legal standards. Similarly, dealers of scrap metal who possess their own scales must also adhere to the standards required of weigh masters, as they are often required to provide certified weight slips. Hay dealers selling baled hay by volume may also take weight into consideration, but by providing services that include weighing and selling based on weight, they align with the definition of weighing in trade.

Thus, the distinction here lies in the fact that common carriers generally facilitate transportation rather than weighing for official purposes, thereby not qualifying as weigh masters.