Urgent purchase advice /8 W115

Hello people, I was offered a /8 today. Since I don’t have much idea of the market situation yet, I wanted to ask how realistic the price is. 200.4 Gasoline year: 1974 120.000km 1st hand, checkbook complete with MB, including all invoices Zero rust Interior as new, as always already covers were used Pure summer and garage vehicle Condition Technology 1 Condition Lack 2 Condition Interior 1-2 What would be a fair price for both? Wouldn’t like to knock the old man over the ear and enter a pay fair price. Thank you!!!