Odd depression in wheat penny

I'm going through a collection of wheat pennies that I inherited and found one that has an unusual mark on the reverse. It's a small hemispherical depression, about 1/16th inch in diameter, about half that in depth. The diameter is not perfectly circular. The surface around the hole is not raised, like I would expect if a tool did this. If I had to guess, I'd go with chemical caused.
The penny is a 1909 (no mint mark).

Has anyone seen anything similar before?

 

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yea pennies made excellent bb gun targets back in the day...

 

I've got a punch set you can borrow if you want to make your own. Cheaper than BB's.

 

But not as much fun!

 

But with a punch you don't have the danger of putting your eye out.

 

That's why I have safety glasses... bing, bing, bing...whoops there goes another one. Got a squirrel that time!

 

Actually no deformation on the other side. Doesn't necessarily mean a bb couldn't have done it. Seems like a plausible explanation.

 

Well that's why when posting a coin you post both the obv and rev sides of a coin. Buy a pack of BB's and place one in the dent betcha perfect fit.
As for the obv. Side view no deformation that would depend on distance , and foot pounds of the bb striking the target.

 

The difference between an old Red Ryder and a new 2000 FPS Crossman.