MoD Specs

Hi boys and girls got a quick question fro you lot in the know, what was the difference between the Series 3 109" 3/4 GS and the Civi 109" and what tyres were they fitted with originally.
My MoD Landy has 7.50/16 C tyres and they say Good Year Cross Ply and i have reason to believe they are the original's, but i dont know the model.

Thanks