How much would a pinball machine from the sixties be worth?

Alright so my dad has this old chinese pinball machine (from the 60's) and I was wondering how much it was worth. It doesn't have the because my dad got it when he was a kid and lost them. Other than that, it is in GREAT shape. So how much do you think it would be worth? Thanks in advance. It works, it just doesn't have the . We are going to buy the . How much would it be worth then?