I promised a write up on miscuts, sorry you have had to wait, but I have been busy of late with other projects and packing for my move.
Better late than never so here we go with a short description on what to look for.
People often confuse the word "miscut" with a miscut stamp or booklet cover, when in fact the term refers to the actual contents of a booklet. Ie: where the pane has been miscut.
Miscuts booklets should be removed by the quality control staff at the printers, but as with all errors some are bound to escape their attention and do slip the net. These find their way into the philatelic market and are highly sought after by collectors of booklets and panes, some are quite scarce and hold premium catalogue prices. They also make a nice display when housed and written up with the normal cut panes.
Above a miscut booklet showing the cut line in the centre of the pane
Below a normal cut booklet with lines at top and bottom
Most miscuts are easy to spot if you know what to look for, normal cut booklets have a guillotine line on both edges of the pane ( known as the cut lines). Most miscuts on the other hand show the cut line in the centre of the pane.
Miscuts are also known where they alter the se-tenant combination of stamps. These carry a bigger premium over and above the norm and command very high prices, some are in the £100s.
Do you have a collection of booklets tucked away? If so I suggest you dig them out and get checking the contents, its quite possible you have something of value that was thought to be a run of the mill item.
Good luck and keep em peeled.