In addition, tell-tale signs the traveler is not from Oceania would be his/her facial features and the way he/she does not guard his/her emotions.  All members of the Party have become less than human and guard their body language, facial features and reactions religiously so they will not be arrested for thoughtcrime.

Only the Proles are "free" enough to show their emotions, but with this freedom comes their oppression of the Party who keeps them barely alive through businesses which will never thrive.

In Orwell's Oceania, people might be able to identify travelers by their familiarity with (and perhaps attitude towards) the principles of Newspeak, their attitudes towards Big Brother, and, probably most easily, their attitudes towards the past. Not having been present for the Party's ongoing edits of the past, travelers would not know what had been erased and what had not.