Do not know what it is, but it has the following inside the zip file:
1) META INF folder
Sure does not work for fastboot!!! I found a zip on here that had the right file name and was odexed. Downloaded, checked the md5, then unzipped to read the Android-info.txt file. All looked right. Made a backup of phone and loaded it on in.
Succsess!!! Of course I had to put TWRP back in and root the phone.
So, brief sequence of what I did:
1) OTA update from 4.3 to 4.4.2 caused problems with applications
2) Phone in stock form with Hboot 1.56
3) Unlocked phone - HTCdev website used
4) Rooted phone with SuperSU and installed TWRP
5) Played with ROMS and did not like any of them, decided to revert back to 4,3
6) Phone would not S-off with stock ROM using Rumrunner
7) Ended up with the combination of Android Revolution HD and Firewater. Used my UBUNTU Linux to perform S-off.
8) Back-up performed
9) Used zip file and fastboot to load 4.3
10) Now have Hboot 1.56 with 4.3 unlocked, stock Hboot, and S-off.
Thanks for listening to my rantings.
Maybe this will help someone else with an AT&T HTC One.