Which polar Explorer to seek?

[ReclinerTimer]

So the polar Explorer has always sung to me, even a few years back when some kind of viewed it as an ugly step sister of the Rolex lineup. I'm find myself feeling more and more inclined to pull the trigger on a used one. However, I'm not too familiar with the references or what I should look for. I would get the 40mm and obviously make sure it checks all the boxes and doesn't have a service dial, service hands, etc. With that being said, can anyone help me with specific references of the polar Explorer or maybe explain the difference between certain references? Thanks!