(6) The position of (C) [ = (B)] being 52.0 x 31.0 and of (b) [ = (C)] 49.0 x 25.0 presumably (B) comes from U-531 and (C) from U-668. This enables us to put the signature LK in (B) and PJ in (C).
(7) We now have these cribs
(8) None of the underlined letters are reliable. (i) The German operators often became confused about the order of letters 6, 7, 8 and put them in order 7, 8, 6 instead so we avoid these letters if possible. (ii) The temperature digits 15 in message (b) are unconfirmed and look too high so the K in (c) derived from them may well be wrong.
(9) True decode, compared with cribs
As the only wrong letters are some of these that we distrusted and would not have used on the bombe we should have broken the day's key on these messages.
23. From November to March work continued on Shark on these lines and most of the traffic was read, a good deal of it currently or almost currently. On March 10th the W W book changed and we were faced with the necessity of finding a new way in.