[AJD] 1020 Question

[Chas. C.]

I have a question about a 1020 that I own jointly with my brother. It was once my dad's and after he passed away it was left to the both of us.
My question is I note in the operator's manual it lists this tractor as being either RU, HU, or LU. What is the difference and how can I tell which we have. This was prompted because we are trying to determine the weight. There seems to be a 600 lb. difference between the RU & HU and about 300 lb. between the RU and LU. 
Also, does anyone know what a loader will add to the weight.
Charlie