One of the most famous GVI printing flaws catalogued by Gibbons is the 'Davit" which appeared on the 11/2d and 2/6d "The Pier, Georgetown" duties. It occurs to the top left of the pier R5/1.

Also on this example, from the 1953 printing, are a black horizontal line, printer's guide marks, an inscribed red cross and parallel angled short black and red lines.

Purchased from a dealer in Leeds I have also seen an example in the Murray Payne magazine.

Altogether an interesting study item.