The American Petroleum Institute (API) is the body the writes the API 4F and API 7k codes that govern rig mast, derrick and drawworks design. They also have a quality (opt-in) program for manufacturers to gain the ability to monogram the product signifying that it complies with all aspects of the API code.
This quote was taken off the API website:
“The American Petroleum Institute (API) is the only national trade association that represents all aspects of America’s oil and natural gas industry. Our more than 550 corporate members, from the largest major oil company to the smallest of independents, come from all segments of the industry. They are producers, refiners, suppliers, pipeline operators and marine transporters, as well as service and supply companies that support all segments of the industry.” (http://www.api.org/).