I am not a Scottish Postal History expert, but I am sure that the Scottish Wheel Tax applied to all mail within, to, or from Scotland and is usually a hand stamp such as yours, but sometimes added in manuscript.

Winston, to be honest I am not sure. I cannot see anything on the front, either under glass or on a high res scan. But there is something visible on the reverse (that I had not noticed)

Happy to adjust the price if you were interested.

Steve

Any/all combination of watermark and perforations.

Happy to purchase or exchange for similar

Spec AS15c. Variety double 'D' completely visible. Four good margins, no faults. Scarce cancelled by black MX. Catalogues £650 as such.