Need Expert Advice On A Trade Dollar.....

I would not discount the possibility that this is Breen 5823, however the mintmark placement is not a sole qualifier for authenticity by any stretch. What are the circumstances of your involvement with the coin? Do you have the means to make other qualifications without financial risk ?
Breen 5822 has similar position on the horizontal plane, but with left C shifted slightly lower than right C.
(Breen 5822 is the 1878-CC plate coin from Bowers "Silver Dollars & Trade dollars of the U.S.")
Both of the above varieties have left C below space between N_S of GRAINS.

It could be authentic but I don't like how the letters stand out so much. They really pop out compared to the D in dollar. In other Trade dollars I've had the mint mark wasn't so perfect. That being said, the placement is very similar to my 1875-CC.