Question: Is there a standard library barcode identification system?
Answer: The short answer is "no". There are many barcode registries, including one called the "National Barcode Registry". However, this registry only contains a fraction of all library barcodes in the United States and Canada, mostly those libraries that formerly used a system called GEAC, which is now maintained by Infor. You can still obtain a new, unique prefix assignment from this company, but you need to call them, as the service is not available online.
There are several types of barcodes in use in libraries, as well as RFID. In most libraries, the first digit of the barcode indicates whether the code is for a patron or an item. The next4 digits are the library identifier. Since there are only 9,999 variations to this 4 digit ID, and there are many more libraries than that in the US alone, there is bound to be some overlap of these codes.