Yes, we have seen them before. I can tell you that in most shops these stickers are not accepted. In one shop in particular, there is a photo copy of the first sticker with a note not to accept them. If you read the language, it is incorrect anyway. Many have been turned down with these stickers. People were buying the tanks online through leisure pro then buying the stickers.
Of course I am sure that many shops have no idea and accept them.
In my limited experiance, "most shops" is a gross overstatement.