If you have a look at the reticle options the standard view can be changed to show what info you see on it.
When you mouse over any tank you should be able to see what % hit points they have left, tank type etc.
The picture shows a reticle I haven't seen myself, but as said above it prolly has to do with being fully zoomed in.
Don't think there are any mods and besides if it is a mod, the only thing different may be the circular reticle, but as I'm not a home I can't check the reticle options to see.
Where are you seeing the tank tiers by the way? Can't see what you mean.