ALE MET MOP BLM
BAG CAP YOU CLT
IRE OIL LUG LNR
NAY BIT BUN BPR
AIM BEY RUM GMY
OAR GIN PLY CGR
PEG ICY TRY CMN
CUE COB TAU PNT
ONE GOT PIU
The fifteen letters used are A, E, I, O, U, Y, and B, C, G, L, M, N, P,
R, T. The number of words is 27, and these are all shown in the first
three columns. The last word, PIU, is a musical term in common use; but
although it has crept into some of our dictionaries, it is Italian,
meaning "a little; slightly." The remaining twenty-six are good words.
Of course a TAU-cross is a T-shaped cross, also called the cross of St.
Anthony, and borne on a badge in the Bishop's Palace at Exeter. It is
also a name for the toad-fish.
We thus have twenty-six good words and one doubtful, obtained under the
required conditions, and I do not think it will be easy to improve on
this answer. Of course we are not bound by dictionaries but by common
usage. If we went by the dictionary only in a case of this kind, we
should find ourselves involved in prefixes, contractions, and such
absurdities as I.O.U., which Nuttall actually gives as a word.