buying a golf need advice
 

Hi all my name is dave and am looking at buying a second hand golf, i have seen a 1.9 diesel 2002 model on the back of the car the badge is just a D not tdi however when the bonnet is lifted the engine cover says 1.9 tdi, so what i want to know is why would it just say D on the back and not TDI i would be grateful if someone could clear this up for me as im confused thanks