I'm not sure that there is a "standard" for leg bands. Certainly over here in the UK it's very difficult to find any useful information to help decipher or trace them. I don't think there's any specific information that needs to go on a leg band or any particular order so a lot of breeders tend to make up their own systems, making it harder to track where a bird has come from or how old they might be.
The numbers/letters on Alfie's leg band were pretty much unreadable as time went on. I have a record from his 'hatch certificate' which says what was originally on it but I wouldn't have been able to tell you otherwise. I ended up having to have it cut off after several years because it was starting to irritate him and was making his leg sore. So I had it cut off and had him microchipped instead. I did keep it in my purse for the longest time but unfortunately I think it must have fallen out at some point as I no longer have it.