The coal load and tender deck actually are one piece. I have converted a few of these to oil burners.
The back, angled coal board will come off with a tug. You will then see a slot that the coal board covered. Insert a jeweller's screwdriver and GENTLY work out the thing.. Sometimes, toothpicks' pushing out the sides help, sometimes, they do not.
I am assuming that you do not want to damage the coal load. I did not care, as I was removing it and replacing it with an oil bunker.