

Stacks Bowers is a well known and respected auction house/dealer in the industry, but I have no personal experience with them.
Whether or not $800 is a fair offer really depends upon the condition of the note. With 3 light folds and no other issues with the note, it would probably grade as extremely fine 40, maybe 45. If I counted correctly, Heritage Auctions has sold 9 series 1934 $500 notes graded by either PCGS or PMG as EF40 in 2018. The auction prices ranged from $1,020 - $1,260 with an average price of $1,126.
If you went the auction route and got your note graded then there would be costs involved. Probably 5-10% seller's fee (it's negotiable) and maybe around $60 to ship the note to HA and have them get it graded. So, IF the note graded EF40 (could go higher OR lower) and IF it sold for an average auction price (again, could go higher OR lower), then you MIGHT get $950 for the note. Also, going this route takes time and it could be a couple of months (or more) before you actually got a payment.
So, there are risks and time involved in getting the note graded and auctioned but you could end up clearing more than $800, or then again you might get less.
If you're a risk taker, and time isn't that much of an issue, then you might want to get the note graded and auction it. If you're risk averse, then IMHO that $800 offer is a fair offer.
Best of luck with your decision
