I've seen them before but never bothered to work out what the second letter meant. I'm sure it is a date code but the second letter has to have a meaning. Cast parts normally have an A, D or N for the shift I believe but remember these plants (foundry in Victoria vs panel pressing/assembly in South Australia) are far removed from each other and given the body plants can't even be consistent with their body tags I doubt the other facilities would be consistent with date markings.