I'll go with an estimate of value, based upon a similar Bally of the same year. As Bally used wood rails there isn't a problem with corrosion as is evident on your machine. Backglass and playfield look nice. I can't see the cabinet condition and artwork and I can't tell if the legs are original to the machine or even on the machine. I can't see a coin slide.
I will estimate 280 euros max. and would buy at 150 euros.
Rarity doesn't improve value unless it is paired with demand.