If the image is installed using the BootROM
method, then the file is renamed rescue.xos internally, during the process. The show version output will display the filename as rescue.xos instead of the original filename used. Installing an EXOS image can be referred to as Rescue or Recovery mode, hence the filename. When performing an install within EXOS, the file will be named identical to what is used on method used to transfer and install the image.
The above output example shows that slot-1 was upgraded using the BootROM, whereas slot-2 was upgraded using EXOS.