What is the method used to recover a serial number when it has been removed by grinding?

• A. Grind area smooth, polish, apply acid
• B. Sandblast
• C. Polish only
• D. None

Answer: (A)

When a serial number has been removed by grinding, the goal is to expose what lies beneath the surface by preparing the metal for a revealing chemical contrast. The correct method starts with smoothing the area to remove the roughness from grinding, then polishing to create a uniform, reflective surface. This preparation is essential because it lets the subsequent chemical etching act evenly. Applying an acid etchant then reveals the latent marking by differentially dissolving the metal around the original stamp, causing the numbers to stand out again as a visible pattern. Without smoothing and polishing, the etching would be uneven or fail to show the buried characters; less suitable approaches like sandblasting would destroy the surface details needed for a clear reveal.