1
general::
Seemingly, based on available evidence, as in On the face of it this project should break even in six months. This idiom uses face in the sense of "a superficial view." [Early 1700s]
American Heritage Idioms
2
general::
Phrase(s): on the face of it
Fig. superficially; from the way it looks. • This looks like a serious problem on the face of it. It probably is minor, however. • On the face of it, it seems worthless.
McGrawhill's American Idioms And Phrasal Verbs