Usually when a previous owner leaves a piano behind, it's because it's worthless or damaged beyond repairs that make economic sense...but hopefully I'm wrong.
How tall is it?
If you use a free chromatic tuner app, what frequency does it say the A above middle C is? How about the one above and below that?
If you open the top, is there evidence of mold, water damage, smoke, rodents, etc.?
Try giving this article a read, and checking your piano the same way:https://www.pianobuyer.com/article/how-to-inspect-a-used-piano-before-buying/
If all that looks good, it would probably be worth hiring a tuner to tune it and then let you know what state everything is in.
If the tuner's report is positive, you can use that information, and list "freshly tuned" in your ad to get a better selling price for the piano.
Most 50+ year old uprights (yours was sort of average quality from a fairly established brand, which had been bought by a big piano-making conglomerate) are worth anywhere between $0-$500. But it depends mostly if they're tunable, all the keys and pedals work, and it doesn't need anything significant in terms of repairs. If all those things are true, and the piano was freshly tuned, then I'd say $500 is a fair maximum price. Most pianos would be worth less.