If this piano has been tuned regularly and in great condition, with original matching bench, is is most likely worth anywhere from 600 - 1000 dollars. Depending on your local market, the price may vary.
The cable piano is not a really big seller right now. As of the pricing, they are so in and out of bounds that no one can keep a average pricing on them. Online, the lowest price was 200 and the highest was 2000.