Before you send it in for a certificate, do not remove the stamp looking for the watermark. If removal is needed you will be advised. Paper color being incorrect would remove the need to soak off for watermark detection.
I am also bothered by the light cancel not extending off the stamp.
The last issue is the bold cancellation is not contemporary. That means the retail value will not reflect the on cover price in the catalog as well as the off cover, simple used stamp.
It is your stamp and your certificate money, just report back any outcome.
