Although Royal Mail's prestige book FDCs have only a part of the Machin pane, early prestige stamp books were produced with no clean way of separating the pane from the book. Later panes were produced with rouletting against the binding edge, and later still a second set of rouletting just to the left of the stamps. (Most notably this meant that the official FDCs for the wilding pane of the 'Gracious Accession' PSB had only 8 of the 9 stamps on the pane, because the 2nd class red, with the diagonal watermark, was to the left of the right-hand rouletting.)
As many people know, registered dealers can buy loose panes from prestige stamp books, which enables us to service FDCs without having to remove the stamp panes from the books. This is why you often see panes with no stitching holes in the left (binding) margin. (These panes should not be available mint as they are supplied only for covers.)
The loose versions of pane 1 from the ToA booklet are markedly different to those in the books: they have no rouletting at all. This ought to be mentioned in some of the more specialist catalogues.
My 50th Anniversary columns for Linn's Stamp News - For my last Great Britain columns for *Linn's Stamp News*, I decided to go out with a bang and summarize the history of the Machins in a format that would...