NavList:

Hi Alan,
I was thinking of doing the same thing with the same H.O. 214 volumes but inertia took over and they are still on my shelf - along with a second set. I was tracking eBay prices and they are not as high as they should be. Today on eBay they vary from a low of $5 per book to an average of $10-$15 with shipping. There is one listed for $28 with shipping. I'd be tempted to select a mid range price, perhaps add a bit for a set, and print the eBay summary page to keep in my records.
You might find some higher prices at used book sellers. I'd feel confident using any reasonable numbers as long as I could find several examples. $100 to $120 ?

My only real experience was in donating a money bag to the New Orleans mint. I contacted a dealer in such and told him what I was doing ( so he didn't think I was going to sell it). He graciously gave me an estimate in writing.
I had asked the N.O. Mint for an estimated value and they said that they were prohibited by law from setting values. They did agree with "At least that much" on the dealers estimate ( $750) and sent me a note/confirmation/receipt for my taxes.

I think I've seen exactly one Vol 9 of H.O. 214. I'd think that Navy ships would have a complete set and Vol 9 wouldn't get much wear.
Regards, Noell