Thanks very much for the input. After more research at the site Burnside Bob recommended, plus looking at other examples for sale at HipStamp, I agree with you; what I have here is two copies of # 9. What helped convince me was seeing a copy of #8 at HipStamp on thin white paper, and seeing an example of # 10 on ordinary white wove paper there also. Both of those stamps are on paper that is clearly whiter than either of the copies that I have. By the way, I went ahead and bought this copy: https://www.hipstamp.com/listings/l...ing/31028281
of # 10 from MikeAldrich stamps on HipStamp this morning. It was only $20, and a nice clean example in relatively good shape. I have bought from Aldrich before, and trust their judgement.
I also agree that the blue cancellation is unlike any that can be seen on any of the sites. There seems little incentive to forge a cancellation on this stamp since the catalog value is the same mint or used, but getting another opinion would be helpful. So, I have decided to send it in to APS for expertizing. The $25 fee is more than I paid for the stamp a year ago, but even with the damage to the stamp, I think it will be worth getting a certificate.
Burnside Bob: Thank you very much for the link to Post Office in Paradise. I spent several hours last night looking through their wealth of information on Hawaiian stamps. I also wrote to Fred, sending him a scan, the link to this post, and asking his opinion. He declined to offer one and suggested that I send them to APS for expertizing. (I am a long-time member anyway.) He had a good point about identifying subtle color differences from scans, and measuring paper thickness. So I plan on sending the right stamp to APS, that way I can also ask their opinion of the odd blue cancellation.
Once I get it expertized I can revisit this post and let you know what APS says .
Thanks again for all of the help!