Scott 551 NY Precancel Items

Just found this one in a stack of NY precancels. Looks like it "slipped" when it was precanceled:



Also, on the same issue, I have come across a couple of these. This one happens to be an invert, but I'm curious about the double versus single line. Is there a specific precancel type that accounts for the difference in single bottom line versus double top lines?



Any comments would be welcomed. Thanks.