Polo I - single vent, 2 button (full, traditional cut)
Polo II - double vent, 3 button (traditional cut, but 3 button and side vents can make it look slimmer than Polo I)
Polo III - double vent, 2 button, ticket pocket
Polo IV - double vent, 3 button, ticket pocket (slightly higher arm holes, so feels trimmer about the chest)
Polo I-IV suits generally have pleated pants (traditional Dalton model)
Hacking (jacket) - side vents, 3 button, like Polo II, but with angled...