DOT stands for department of transport. It's the US body. I have no idea what Aussietig is asking you.
I'd be more interested in seeing if the manufacture dates are within a few months of each other.
re: the Bob jane guys comments. He's trying to put the wind up ya. No tyre shop likes fitting tyres bought elsewhere - we used to refuse to fit tyres we hadn't sourced as it p!ssed us off so much that we'd lost a sale (we used to sell at $1 profit just to deny our competitors a sale). If you do get vibrations then I'd be wondering if he actually balanced them properly.