Which of the following is an example of an alphanumeric symbol used for export control classifications?

The designation "5A992.a" is a valid example of an alphanumeric symbol used for export control classifications because it conforms to the standard format for Export Control Classification Numbers (ECCNs) under the U.S. Bureau of Industry and Security (BIS). The format typically consists of a category symbol followed by a number, and sometimes a subcategory designator, as seen here.

In the case of "5A992.a", "5" refers to the category of the item, "A" indicates the type of product, "992" specifies the specific control within that category, and “.a” further clarifies the classification. This structured format allows for the clear identification of the commodity, technology, or software subject to export controls and is essential for compliance with export regulations.

The other options do not follow the established format for ECCNs. "ECCN 202" lacks the specific structure required, while "XYZ123" and "AB4567" do not correspond to any recognized classification system for export controls. Thus, "5A992.a" stands out as the proper representation of an alphanumeric symbol for export control classifications.