The front of the insert can be distinguished from other sealed English Ancient Mew inserts by the phone number.
PS/off-topic: If anyone comes across any of the legendary birds (especially Moltres) with Danish insert (the Ancient Mew front of the insert will likely be Catch Mew!, but the back and phone number are likely the same - I’ve never seen the Danish legendary birds, so I’m not entirely sure), please lmk as well.