Let us say that some enterprising and foolhardy scholar with a minor magical talent has decided to fake being a magus and infiltrate the legendary and secretive Order of Hermes for some reason. He already speaks Latin and has a good Artes Liberales, and some Philosophy (otherwise he isn't much of a scholar).
He presents himself as Master Mimicus at a local covenant (somehow; in some sagas there are covenants that are, so to speak, out of the closet), asking for a few days of hospitality, explaining that he is from the other side of Europe, and does not speak the local language. That's not a serious issue, as the magi may well use Latin as their common tongue and there are probably a number of servants who have enough Latin to cope with their masters.
The servants and companions may note that Mimicus is not an off-setting sort (presuming he isn't afflicted such with a Flaw), the way the magi are, but it's possible that's not so odd, especially if they've dealt with Jerbiton magi. Redcaps are also magi (socially at least) and they don't set people off. The magi will not notice this; the Parma Magica screens the effect of the Gift out.
Mimicus has no OOH Lore, and probably does not think to give to give the name of his master; that's a little odd, but not very odd. There are magi who don't refer to their parents, for various reasons. Mimicus probably doesn't name his House either, unless he's done a fair amount of research and learned the names of Houses. This would be very strange; most magi formally introduce themselves by name and House. Here, Mimcus is in direct danger of being suspected.
Worse yet would be to name a House that he does not reflect: A Flambeau with a meek attitude in plain brown robes, or a Criamon in rich silks and a full head of hair with no visible stigmata and who speaks plainly, or espouses straightforwardly ordinary Christian philosophy. Now, he's in trouble.
Mimicus would have to set himself up pretty carefully to pull this off. He might be able to claim great ignorance of the Order as a new recruit; maybe the magi ask him helpful leading questions, but it seems like he's dancing in a minefield.