When "They" (of "Them") first ring the house the telephone ringer is the classic European electronic bell signal from the last thirty years or so. However when Clem answers the phone the device clangs like an analogue phone would have sounded from the phones of 70 years before that. Then again, when she puts the receiver down, it clangs again like an antique phone.
Right after Clementine removes the piece of glass from Lucas' leg, there are repeated shots of the bedroom door as the intruders try to get in. During one such shot the handle that had just busted off reappears, intact. In the next shot of the door the handle is once again missing.