I picked up the item above on eBay not long ago. It is cut from the press sheet containing 12 Diamond Jubilee souvenir sheets (one of which is pictured below).
There’s not too much to say about it, other than it is an unusual piece. It ties a Machin with a Wilding-type design, and it’s a nice piece to include with the other Diamond Jubilee stamps.
PS Does anyone know why the rows of perforations were inserted between the individual souvenir sheets?