Dr. Philip Bouffard, a forensic document specialist in Georgia who has compiled of database of more than 3,000 old fonts, said people who bought the I.B.M. Selectric Composer model could specially order keys with the superscripts in question. Dr. Bouffard said that font did bear many similarities to the one on the CBS documents, but not enough to dispel questions he had about their authenticity. A spokesman for I.B.M., John Bukovinsky, said he knew only that it introduced proportional spacing to some typewriters in 1944, most notably in the Executive line. At Lexmark, a spokeswoman, Maria W. Gambrell, said typewriters...