All OEM 903 and 953 inks are programmed with a bunch of electronic serial numbers on them.....printers that take 903 and 953 cartridges have a system of registering and remembering those serial numbers. If a printer detects a serial number from a compatible cartridge that its seen before it will initially reject the cartridge.
This doesn’t happen with oems as there are hundreds of serial numbers on each cartridge, so it will never happen that you get two with the same serial no.
The compatibles however can only have a few serial numbers on each chip batch that's produced.... 5 to be exact. So the chance of having one duplicated is slightly increased.
if it happens your user will initially get a failure message.
HOW TO FIX
the next step is to reinstall the cartridge again. This rotates the serial no. Users can do it up to 5 times EACH INK. This usually solves any issues, as its unlikely your customer has changed the inks that many times that their printer has seen all 5 serial numbers on each of those cartridges before.
So its vital that if they get a failure message or non recognising cartridge you must ask get them to take the offending ink out and reinstall it at least 5 times. To be sure that its attempted all 5 serial numbers on each cartridge.
If they still have a failure its best to exchange the ink, as its likely that the replacement can be from a different batch and therefore have 5 more difference serial numbers on it.
The chips have a number on (1 ,2 or 3 for example). If you do exchange, simply make sure you exchange for one with a different number on it to the other.
THE NUMBERS ON THE CHIPS DO NOT REPRESENT A VERSION NUMBER. IT IS A WAY OF MAKING SURE YOU ARE NOT USING CHIPS WITH THE SAME 5 SERIAL NUMBERS ON AS BEFORE.