That determines most of "B" and "E", and there would only be three possible variations left that pair (ujd) and (mqa). There are still 20 possible variations for "C" and "F". At this point, the Poles could decrypt all of the first and fourth letters of the daily keys; they could also decrypt 20 out 26 of the second and fifth letters. The Poles' belief in these permutations could be checked by looking at other keys and seeing if they were typical keys used by code clerks.