( informal ) used to say that sth seems to be good, true, etc. but that this opinion may need to be changed when you know more about it :
On the face of it, it seems like a great deal.
ON THE FACE OF IT
Meaning of ON THE FACE OF IT in English
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005