It appears the two killers are struck 180 rotation to each other. Assuming the cover to be "upright", I have rotated the loose single and added some lines. Note the near-alignment of the blue vertical line across the points. Similarly, the jogs in the pairs of orange and green lines needed to connect them up across the points of the flag.

This would not be unusual since the killer is (apparently) not duplexed to the CDS.
As an aside, I am always intrigued by claims of:"one of x known", without any reference to who or what society or auction house is doing the census work - seldom the quality or level of confidence one gets compared to a R. A. Siegel census with illustrations and citations to certs and previous sales. Just saying.