Ask the owner for the VIN; he doesn't need to give the full number, just the first few digits will be enough to confirm if its an import or not, and if an import, which market it was intended for.
External body checks are not foolproof; a significant number of imports imported 1997-1999 were retrofitted with UK rear panels; Donutz did a roaring trade (at one time rumours abounded that the import square plates were going to be made illegal). Neither isthe boot stop lamp, as boot linds can be swapped, or the interior power window switch, which on a 1993 import will be different from a UK 1993. VIN is the only sure fire way; send me the codes off the drivers door shut, and I'll work out the original package as well.