Well, companies often tried to save time with folding the stamp sheets - that's why you find many mirrored or inverted perfins.
Sometimes the stack got too thick for the machine, so the last stamps could not be perforated completely ... or in this case the letters were just embossed into the paper.
Most collectors see those as normal perfins and keep them, until they find a nicer one.
Now to the WILLS: Catalog number:
W D & H O Wills, Branch of The Imperial Tobacco Company (of Great Britain & Ireland) Ltd, Bristol 3.Postmarks:
Mainly Bristol. Also Belfast, (Ca)rdiff, Chelt(enham), Glasgow, and Liverpool.