1999 P Nickel Machine Doubling ?

Yes you are correct--shelf-like and serving to reduce the width of the devices means Machine Doubling.

yes MD on all the letters, BUT, there is also a die chip above the bottom horizontal bar of the 'L'

I am going to have to disagree with the diagnosis of Machine Doubling. To me, that melted butter look is classic Die Deterioration Doubling. You can see soft rounding and radial flow on both the obverse and reverse, consistent with late stage Die Deterioration. Examine the second DDD example on Error Ref, which just so happens to be a 1999 nickel:

https://www.error-ref.com/?s=Die+de...ion+doubling

The devices on this nickel look a little withered and softened, but they are arguably the correct device width compared to an ordinary nickel. I have yet to see examples of machine doubling—either push or rotation—where the sheared metal wasn't a steep edge from the parent device.

https://www.error-ref.com/?s=Push+doubling

Also, as someone who CRH nickels with a magnifier, I can state from experience that recent nickels do not often display classic Machine Doubling, but lots and lots of them show Die Deterioration like this example. For whatever reason, from about 1997-2003, the U.S. Mint just ran their nickel dies into the grave.