At present the study of watermarks has not reached a stage at which they
are able to contribute scientific proofs of high importance, nor will
any proof be ever deducible from them except the earliest possible
occurrence of an undated issue, although probabilities of concurrent
printing may be arrived at. Only some plain facts, therefore, will be
stated with respect to their occurrence in the early Oxford books.
If we take the first group (the Jerome, Aretinus and Aegidius), we find
no less than 26, out of a total of 50. The Rufinus has seven (two shared
with the others, one shared with the Aretinus only, one shared with the
Latteburius, and three peculiar to itself). The Aretinus has 22, most of
which are found in the later groups, but eight are peculiar to itself.
The Aegidius has two only, common to the group.
In the second group (Cicero, Ales, Latteburius, Latin Grammar) there
appear to be 28, of which four are common to all the groups, one is
shared only with group one, seven only with group three, and sixteen are
peculiar.
In the third group 38 occur, four of which are common to all the groups,
nine are shared with the first alone, seven with the second alone, and
eighteen are peculiar.