On June 19, 2013 I was pleased to purchase for 205,250 GBP (about $316,000) at Bonham's in London
the copy of the offprint of Alan Turing's On Computable Numbers
(1936) along with the offprint of Turing's Correction
to the paper (1937) that Turing presented to the philosopher R. B. Braithwaite
. This represented a new price record for any published work of 20th century science, a new price record for any offprint, and a new price record for any work on the history of computing. The offprint of On Computable Numbers
was inscribed to Braithwaite by Turing; the offprint of Turing's "Correction" was signed by Braithwaite. Documented in the standard biography of Turing by Andrew Hodges, this is one of the most famous copies of the most famous theoretical work in the history of computing. The pair of offprints was later presented by Braithwaite to the English philosopher Timothy Smiley
, who may have been the consignor. Turing received and distributed very few copies of these offprints, so it is conceivable that this set of offprints may be the last complete copies in private hands.