SN9039 sold for $3,499 on eBay, Nov 28th, 2004.
Apparantly this machine was used in the Seattle Center until 1981 when the operator went out of business. It was sold to the eBay vendor and he kept it in his basement, unused, ever since then.
If you look closely at the pictures, you can see the green Seattle Game License sticker in the right corner of the screen area (the license is due to run out in 1981)