There are two subsidiary considerations left. One is that mistakes of
date in colophons are not uncommon. An edition of Aeneas Sylvius’s
©Epistolae© (Cologne, printed by Koelhoff) is dated MCCCCLXVIII, which
is stated to be an error for 1478, and an ©Opusculum de componendis
versibus© by Mataratius, printed at Venice, is also believed to be
erroneously dated 1468 for 1478. Caxton’s edition of Gower’s ©Confessio
Amantis© is dated 1493 instead of 1483. I have noticed the following
additional errors affecting dates before 1501:—720 for 1720, 1061 for
1601, 1099 for 1499, 1334 for 1734, 1400 for 1490 or 1500, 1444 for
1494, 1461 for 1471, 1461 for 1641, 1462 for 1472, 1472 for 1482.
There is no doubt therefore that a mistake of date in an early book has
many parallels, and so far the improbability of it happening in other
books is diminished. At the same time one would expect the first
printers in a place of learning to be careful enough, even if an initial
blunder of this magnitude were committed, to correct it in some copies
before issue. It is of course conceivable that the date was deliberately
falsified, to avoid expected unpleasant consequences of being found
_flagrante delicto_, but this hypothesis may be left to be dealt with
when some one maintains it.