When was the last time anybody has seen one of these for sale?
I've seen quite a few with the silver chrome accents, but haven't seen an entirely black chrome DE for a very long time.
Would this be considered a custom finish to be done at the DE custom shop?

I just want an all black chrome 50.

I don't think Magnum Research ever offered a Black Chrome finish. Years ago I looked for Black Chrome finishing for my Desert Eagle through some of the refinishing companies like Ford's and most no longer did Black Chrome refinishing because it was not very durable. My research indicated that Hard Chrome was a lot more durable than Black Chrome. At that time I bought a nib Hard Chrome Desert Eagle. When the new stainless steel Desert Eagles were released earlier this year I sold it and got one of the new ones. I like stainless steel and the new ones also have a light rail.