The design length difference is in the wrong direction to be a 613. Sorry.
The listing in the Scott Specialized Catalogue of United States Stamps and Covers is a good starting point. The catalog notes that the design of the flat-plate variety measures 19¼ millimeters by 22¼mm.
Because of the way the images were stretched when the plates were bent (or curved) to form the semicircular plates attached to the rotary drum, the rotary-press variety measures 19¼ by 22½mm.
So a ¼mm measurement the long way makes a difference of $39,999.75? Yes.
But sometimes the difference is even less than ¼mm. There can be some variation resulting from paper stretch and shrinkage. The 22¼mm length for flat-plate examples and the 22½mm measurement for rotary-printed stamps are averages.
It is important to remember that authenticated rotary-printed stamps measure as short as 22.375mm but will always be longer than 22¼mm.
A good way to check for this characteristic is to cut a damaged gauge 11 flat-plate stamp in half vertically. Take the left-hand piece and use it to identify stamps that are long enough to be rotaries by placing the half-stamp against your gauge 11 candidates.
Anything longer than the flat-plate stamp needs to be checked further.