When connected in fastboot, type
fastboot oem device-info
And it'll show device tampered true or false
To get it all back to stock, flash the factory image completely then boot TWRP (don't flash it) and run the bootunlocker script found in the Nexus 5 unroot thread
Tampered is set to FALSE, so to return to full stock i just flash the image and afterwards lock the bootloader (fastboot oem lock) manualy.