The below item sold on ebay 29 October for £26.

An absolute bargain price and although i actually forgot to bid on it i probably wouldn't have bid full value as i was slightly concerned if genuine, its obviously extremely easy to forge this but..

Against : Most copies I've seen including complete panes all seem to have a slightly thicker red pen mark plus the tail of the tick is always very free flowing (done quickly) where this example seems very strained and the tail is not completed in one swoop

For : 1) It was not listed as a red tick cover which would suggest it was not designed to deceive (at least not my this seller).. unless the seller was hoping for a more subtle deception. 2) The first part of the tick does look similar to bottom right example in second image.

..again, i am no expert and it's mainly published to stimulate some discussion/thought.