In the Library or Develop module, Command J brings up a window that allows you determine what file information is displayed in the grid or loupe views. Once it is set, back in the grid view pressing just J will cycle through what you’ve set up, and in the loupe view pressing I will cycle through what you’ve selected.
In the develop module, the lower left corner has a “Copy…” function.
The interface that opens allows you copy any develop settings. You might find it convenient to uncheck all first, and then of course copy the crop.
Then select the other image from the filmstrip and press “Paste” (to the right of “Copy…”).
Alternatively, if there are two or more images to match the master, select them all in the filmstrip or grid view (if done in the grid view of the library, return to Develop) and, making sure the master is the primary image selected (its border will be brighter than the others’), copy the crop from the “Copy…” interface and when it’s closed, press “Sync” on the lower right.