Photo Mechanic Plus catalogs can index images on various external drives as well as a computer's main working drive.
If you are looking at a thumbnail or image in Search results or a Collection here are three ways to tell which drive it is on:
1. Select the image in a Contact Sheet. The full path to the image is shown in the status bar at the bottom of the window:
2. If the drive is attached, you can right-click a thumbnail in the Contact Sheet and choose “Reveal in Finder”:
3. Add the {path} variable to the Info Text under Edit > Settings > Set Info Text so that the path is shown in the Preview Window for all your images: