The Helen Oswald North Dakota National Bank Note collection is up for bid at Heritage. Helen was from North Dakota. Helen and her husband Ossie were a fixture at all major shows for decades. Good luck bidding.
I'm not a currency collector, but have a tie to one of the old ND banks. I bought a 1902 note from that bank for a fair bit more than I thought it would go for.
I know nothing about the value of the offered currency, but the prices seems strong to me.