[GreenKeys] What is this surface treatment?

[Larry Goga]

Hello All,

I added this question to a message I replied to this weekend from GreenKeys.  The message thread was about “WD-40” and I received only one reply, which didn’t answer my question.  So I’m sending the question again in its own messsage thread.

In the attached photo you can see a flat metal plate in the lower left corner.  The surface of the metal plate is covered with systematically spaced tiny dimples or “pin pricks”.  I have seen this surface before in all sorts of mechanical devices.  In this case it’s in a teletype machine.  My questions are: what is this surface treatment called, why is it there and what does it do?

Thank you everyone,

Larry, AE5CZ


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