I agree with your valuation. I own a blank version of the manual. A version with a chassis number may be worth more. It is definitely to the current owner of that car, but in the OP's case it doesn't exist anymore.I've never seen an F1 Owner's Manual from an actual car sell - especially not from a car with such interesting history. I have seen blank F1 Owner's Manuals change hands - typically for around £1,500 or so.