Easy to spot, the series I and II (1989-October 1994) models have a gear selector that only moves forwards and backwards in a straight line, the series III and IV models have the "gated" shift lever that has a zig zag pattern coming down from park.
Series I and II style so non interference engines, engine number begins with UCF10 or UCF-11
Series III and IV style so interference engines, engine number will begin with UCF-20 or 21, the series IV has the VVTI engine.