When putting in the codes for the 11th terminal, there are 10 slots to put a code in. However, you only need 5. I would guess there is more to find. Combining codes? Secret codes hidden elsewhere in the campaign? Secret codes in Anniversary Maps? Translating the strange symbols into some sort of letters, and using them to make a secret message? I come here to ask the skilled (or unskilled) skull, Easter Egg, and Terminal finders to search for Anniversary’s secrets… if there is anything else to find. People to search the campaign on every dificulty, search the Anniversary maps, translate the symbols and codes, and just find anything. I feel that there is something to find.
Post if you are going to search, and if you find anything. Pics and videos for proof, and be specific. Don’t keep anything to yourself. The more on the case the better. Good luck.