Apologies if this is already explained elsewhere on the board, but I'm looking for an explanation of the two letter facility grades. For example, my level 5 tower is an EH. I believe I understand that the first letter is the facility level. E is the 5th letter of the alphabet and it's a level 5. How about the second letter? It seems like everyone at my facility just copies someone else for their paper work without actually knowing what they are putting down?