I know how he he made one of the 3 coins dropped to his palm.
Of the 3 coins, the centre and the right coin are actually clam spring together. A probably over sight on his part that he turned the right coin in place and the middle coin move together.
Now, the dropping coin is hidden in is lower hand, so a slam on the table close the middle and right coin together.
In the black table cloth trick, one side of the coin was black, so you cannot see the coin when he flips it over. The bottom coin was actually on other hand. Another way is the cloth has a hidden pocket to slip the coin inside.