If it's that old, you can take some good guesses about it -- Maybe it's in decent condition, or maybe it's going to need some continual work and be more of a money pit.
If you've got a brand new piano, that's lost a lot of value after you've bought it. At least from what I hear. Instrument buying it like car buying. Used is good value and holds its used value -- and a used piano can actually go up in value.
If it's a grand piano, it's different. It's worth whatever a used instrument in that state is worth. I don't think it's the best brand, didn't sound it was maintained in great conditions the whole time, and the age part... Vintage doesn't mean it's better at all. I was starting to wonder if they mentioned the 1800s if all the little extra new inventions were part of the instrument. I've heard about grand pianos from the 1850s but they're not exactly like modern ones.
The price sounds a little high to me. The typical upright I hear about is someone trying to get rid of the thing and they just want someone to come pick it up for them. If that was the case with this instrument -- if it's a dud -- then then the trash hauler in this case is paying $500 to haul away someone's trash.
It's old, asking price is kind of high, exact condition is unknown but there are a few repairs it definitely needs.... Doesn't sound like the best thing to take a chance on. It could be a good find though, but it's still a chance. Maybe it's more worth taking a chance for one or two hundred dollars. Then if it's a dud, they're not out that much.
I got the impression the original poster was really leaning toward buying the instrument, if they haven't gone ahead and bought it anyway. And if that instrument was in someone's family for 40 years that family might be a little attached to it and have some false idea of its value. Then again, the value of the instrument might be right for that area -- If it is crap yet there are no other instruments in that region available and people really want pianos, maybe it really is worth $500.
I'm kind of curious what the original poster actually did. Or if it's being advertised on Craigslist a lot, if they were to wait, to see if the price goes down -- That's a situation I've seen before. The seller wants one or two hundred but no one wants the thing. A few months later they're just trying to give it away.