In the years since 1991, when the Bureau of Engraving and Printing’s Western Currency Facility began operating in Fort Worth, Texas, collectors of current Federal Reserve Notes have grown accustomed to checking for the facility’s “FW” mark on their paper money. Many collectors now seek examples of both Washington, D.C., and Fort Worth notes from each district or block when available.

Some go even further and try to collect all the serial groups formed when production shifted between the two facilities more than once within a single block.