If you are unable to determine an appropriate code for an industry, pick a company in that industry and search for that company in a database, Such as Mergent Online, and see what codes are assigned to that company.
Nexis Uni indexes newspapers, trade publications and other business resources and goes back fulltext into the 1970's. Database provides company and legal infomation.
From the Search page, click on the box labeled Search by Content Type, this opens a list. Under the Companies heading choose Dossier (Company, Executive & Industry). Click on the box Create a Company List. Type in either the SIC or NAICS code in the applicable place and click Create. There is also a link to look up the SIC or NAICS number, should it be unknown. Or click on the arrow to the right of the Get Company Info box. Click on Company Dossier, this opens the same window from above.
Reference USA – This business phonebook from across the U.S. can also show key employees and some financial information. It is very good for data on small private companies. It is the only way to find information on the various locations of a company. Two great features are the ability to modify a search along geographic lines and a Custom Search that can be used to develop a detailed customized directory. Data can be downloaded into Excel.
Choose U.S. Businesses, on next screen click Custom Search, then click Business Type and find the box for Keyword/SIC/NAICS. Select a code to use, type it in and click the SEARCH box. Primary SIC/NAICS refers to the company’s primary business.