Focus stacking is an absolutely great technique to achive good focus on coins, especially with the high relief coins or coins with a distorted shape or uneven surface. It only requires multiple images at different focus points. Then in photoshop they are merged into a single image where each image contributes to the final image with their focused areas.
Load files into stack.
Load all the images with different focus to the Photoshop. Don't forget to select the auto alignment option.
Select all the layers loaded.
From the edit menu, select auto-blend layers.
Choose stack images.
Here you go!