Hello. I really need your help, it's urgent.

My mother is trying to sell my grandfather's old lister engine that was used in a olive press.
I am trying to convince her not do so it because I would like to keep it and restore it one day and since we don't know it's real value she can do a real bad sell.
Although it was stopped many years ago (20years), it still works and still has its tanks.

Can you tell me more about this engine and what is it value?

Here are some images of it : https://imgur.com/gallery/Atr7UPB
http://