There are a few ways to identify which items are in a project box and which box they are in.
You can load the project box itself and look through the list at the bottom of the box. This would be the best way if you know the box in which you want to look, but not the resource you are looking for. Use the 'Resize' button to make the the grid larger and easier to look through. You can also use the quick search box to locate the resource faster.
If you know the resource you want to check but not which box, if any, it is in. Find the resource in Management using either quick or advanced search then look at its information on screen. If it is in a project box you will see that it is coloured orange as opposed to the usual colour, unless the project box is on loan.
Double clicking the line will open the record card. You will then see at the bottom of the record card, a note to tell you which box it is in.