I found a website explaining these locks, but I don't want to post it unless I am allowed. It is on a site called the travel insider. Part of the review:
This is a simple combination lock that securely keeps your suitcase closed, deters casual pilfering, and also shows you if the lock has been opened by a TSA key. These locks might help you prove a claim for damaged/stolen items if such a misfortune occurs.
TSA Issues
These days all checked bags are screened by the TSA, typically by going through a huge mini-van sized 3D X-ray type machine. If the machine thinks it might have seen something suspicious (and the machines have a high rate of 'false positives'), then someone has to open the bag and search through it to resolve the issue.
For this reason, the TSA have formerly been requiring all bags to be unlocked. And, if they came across a bag that had been locked, they'd have to destroy the lock so as to open the suitcase.
They have now agreed to allow suitcases to be built with special locks, and/or add-on special locks to be used with any suitcases - these locks have a dual keying system. One 'key' (either a physical key or a combination lock) belongs to the owner, and this key or combination has many different variations, so that your key is unlikely to unlock the next guy's suitcase as well as your own. But the second key is a 'master' key that only the TSA has (in theory!) and this master key can open all locks in that series. This means the TSA can now easily unlock and relock your suitcase if it needs to inspect it.
If the TSA does open your suitcase, it will insert a piece of paper that tells you they have done this. In theory, if someone else opens your suitcase, they will not insert one of the TSA slips (although it would seem to be the easiest thing for a gang of professional luggage thieves to simply photocopy off a bunch of the TSA notices!).
If, when you get your bag back at the end of your flight, and the lock's indicator is red, you should immediately open it - at the airport. Check to see if anything is missing. If something is missing, and there is no TSA slip, go and see your airline's baggage claim desk. If something is missing and there is a TSA slip, go and see the TSA, or, if you're in a foreign airport, again see your airline's baggage claim people. Your ability to successfully claim for stolen items is greatly increased by the fact that you are making the claim as soon as you received your bag, and by the fact you can point to your lock and show that the telltale indicator is red, indicating someone has opened it.
It also says you should be able to get them for about $20 a pair (at least in 2003) and will be replaced by the manufacturer if it is cut off by security.