So sorry to hear about your family crisis and I hope everything was resolved to your satisfaction.
The ISBN (international Standard Book Number) number you found is the number for the book that came with your organ. It is Gellerman's International Reed Organ Atlas, and was published in 1985, much later than the organ was built.
Wilcox and White began producing this instrument after 1920, so it is no older than that.
Based on your photo, this organ is in rough shape. I doubt it is fully functional, and you already pointed out that the bellows would have to be replaced.
Old pianos and organs have no value just for being old. In other words, prospective buyers are not collecting them; they want to be able to play them. Pianos and organs have parts that wear out and must be replaced. So, old pianos are at a disadvantage in the market.
In this condition, the current retail (replacement or insurance) value of this organ is approximately $800. If you were to sell it, you could expect to get the fair market (private sale or auction) value of approximately 40% of the retail amount or $320, depending on location and actual condition.
I hope this answer has been helpful to you, Pat.
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