System 7.5.3: Revision 2 or Updated to Revision 2

I have a Power Macintosh 5400/120 computer, which came pre-installed with System 7.5.3. However, the About Box states that it is System 7.5.3, Revision 2. I have another computer with System 7.5.3 installed on it, but it does not mention Revision 2. What is Revision 2?
System 7.5.3 Revision 2 is a set of system software enhancements that improves the reliability and performance for the certain Macintosh computers.

Computers that include System 7.5.3 Revision 2 pre-installed will display System 7.5.3 Revision 2 in the About Box. However, if customers install Revision 2 over System 7.5.3, the About Box will display System 7.5.3, Updated to Revision 2.

This distinction in the About Box between Revision 2 and Updated to Revision 2 is to help determine whether System 7.5.3 Revision 2 pre-installed or updated on the computer.

Additional information about System 7.5.3 Revision 2 is available in the Tech Info Library articles, "Mac OS 7.5.3 Revision 2: Overview & Installation" and "Mac OS 7.5.3 Revision 2: Fixes, Updates, Changes".
Published Date: Feb 18, 2012