Odd pits on several new guns

[pgb205]

Bought two SW pistols. One SD40ve and another MP9c.
Both have odd 'pits' inside the slide, something that my old shield does NOT have. The pattern of pits is different however.

Are these normal?

 

[TunnelRat]

They're deliberately done by the factory. I can't remember the reason, unfortunately.

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[Cheapshooter]

Manufacturing code marks identifing what CNC machine, operator, and production period was used to produce the slide.

 

[GarandTd]

I assumed it was where material was removed to balance the slide like adding lead weights to wheels. My M&P22c has them also, but my other auto pistols do not. Must be a S&W thing.

 

[mcb66]

Looks like Brinell marks to me. Not sure why there would be so many. Plus they are pretty close together, usually not good for accurate measurement.