The National Aerospace Standard (NAS) 523 was developed to simplify the complex world of fastener identification. In aircraft manufacturing, a single wing might require thousands of rivets of varying materials, diameters, and head styles. Instead of listing exhaustive part numbers on every blueprint, engineers use the NAS523 code—often visualized as a "cross" or "diamond" symbol on engineering drawings. How to Read the NAS523 "Top" Code

Specify if you're working on a (like Boeing or Airbus).

I can then provide the specific technical details associated with that portion of the NAS523 standard.

5056 Aluminum Alloy (Used primarily with magnesium structures). KE: 7050 Aluminum Alloy. Why You Need the Official PDF