It's the latest forgery of the 1st class gold Machin. When I looked at it yesterday as an actual stamp on the piece of envelope it was clearly 'wrong' - wrong die cut, wrong screening to the head. It is also on very glossy paper, the sort of thing that might be used for labels on some retail packaging, and whilst it has the security slits, they are not right - for example the two parts to not properly line up.
However, the scan shows something we could not see with the naked eye or magnifier, the presence of the letters that make up ROYAL MAIL - or most of them! As shown, it is really quite a crude mimic of the genuine, with incomplete words in the middle of the design, not just at the edges. There seems to be nothing on the head, and very little effort has been made to match the 'overprint' to the genuine - so little effort indeed that one wonders why the producers went to the trouble of doing it at all!
If anybody can match the die-cut 'perforations' to any other label we would be interested to know; likewise if you find anything that appears to be 'wrong' we would also be interested. Many people collect postal forgeries of all periods and countries and would be interested to add one of these to their collections. So far no more than 3 of these have been found.
Update - additional copies have been found with a different - but very similar - die cut. These were scanned on two different scanners, which may account for the difference in appearance of the printing.