HD - My cover is about 1 1/2" thick; the tab on the cover has a small slot to it, but not nearly as much as your cover does; It is lined up very straight, front to rear wise; My cover was like this when I got it; My best guess is that it could be an early model, possibly before Rupp realized it's easier & cleaner to slot the cover; Again, "I dunno" ..... :shrug: