99% and 100% items should have over 100% durability. I was unable to find anything conclusive direct values of this bonus, though i will continue looking. This has always been a thing in DAoC. I belive its something like 99% quality items should have 110% durability and 100% quality items should have 120% - 125% durability. I am not at all positive of these values, but you should be able to repair these high quality items multiple times before you lose any durability. They show 100% until it starts to drop lower, even when its over 100%.
This is link to thread on uthgard where a dev quotes a mythic post. I was unable to find the original. It is the third post. Below is an except from the mythic quote.
"Repairing an item will use one durability for each point of condition lost, plus one for the repair itself. Many items (especially higher end items) have durability above 100, so you may be able to repair it several times before it shows visible durability loss. The quality of an item never changes."
https://www.uthgard.net/forum/viewtopic.php?f=9&t=39593
This is link to thread on uthgard where a dev quotes a mythic post. I was unable to find the original. It is the third post. Below is an except from the mythic quote.
"Repairing an item will use one durability for each point of condition lost, plus one for the repair itself. Many items (especially higher end items) have durability above 100, so you may be able to repair it several times before it shows visible durability loss. The quality of an item never changes."
https://www.uthgard.net/forum/viewtopic.php?f=9&t=39593