Hello, all.  I'm a new member and am seeking a little feedback on an autograph I recently unearthed.  A friend of the family gave me this many years ago.  It is a letter from Andrew Mellon to Thomas M Galey Esq regarding theMellon Tax Trial of 1935.  I was wondering what something like this might be worth and where I might go about selling it in case I wanted to part with it.

Thanks,

—Cormac