If you are looking locally for a licensed and bonded professional to appraise the bicycle for insurance purposes you could inquire at one of the larger Seattle area antique malls for an antique appraisal professional.
It is unlikely that a professional would be intimate with the collectible bicycle market so a value placed on the bike may not be any more realistic than one you could derive yourself from watching eBay but it might go further toward convincing an insurance company to insure the bike.
Not at all local but another source for a “professional” valuation might be Michael Fallon who runs the Copake Auction house in NY that has a special bicycle auction once a year. Googling Copake Bike Auction will get you there.
If you are looking for a considered appraisal of “Fair Market Value” I could discuss that with you by phone and I am local, if I needed to see more of the bike than pictures allow.