Jay is right. This is missing the black plate overprint. Back in the 90's, at least one proof sheet panel (44 cards with die cuts) was sold without the black plate overprint. This card was most likely cut from the proof sheet, or a similar sheet which would explain the condition. Let's see if the Cracked Animals shows up in similar condition. In the 60's Topps printed 264 card double sheets. Each side contained 3 44 card sets. Each title appeared 6 times on a double sheet and die cuts were not identical from card to card.
With the lack of the black plate, the blue die cut lines are very prominent like on many (if not all) of the 1st series Ludlows. It would be nearly impossible, and crazy, for somebody to create a fake and complicate it with such an authentic looking blue die cut line when a copy of a normal Ratz would not reveal much, if any blue die cut line.
I have several 2nd series stickers with missing black plate overprints, along with a number of 1st series stickers with partial or lightly inked black plates that have the same brightness and appearance of this Ratz. Now if it had #4 on back, there would be a problem.