How do tell the difference between coil waste & rotary press sheet waste?

Both Scott 594 and 596 are four and five figure stamps and extremely rare. Without certification your stamp will obviously be dubious. I suggest it is more likely a Scott 552. If you truly believe it is one of the very rare versions you should submit it to an authentication service like PSE, PF or APEX. Even if you posted a good scan nobody here could definitively measure the design or proof the stamp.

 

The expertising costs are what they are. While you may disagree with the Quick ID certification you are free to submit the stamp again to the APS or try some other service. While no service is 100% they are in the business to be accurate and thorough. If in the odd circumstance that Quick ID was wrong about the perforation the odds are unlikely that they are either of the rarities.

I have taken a good look at the scan and I believe the top and bottom perfs to be faked. It looks like someone has taken a stamp that had a natural large straight edge at the top and reperfed it as well as reperfed the bottom. Take a good look at those perfs with a 30x magnifier and I'll bet you come up with the same conclusion.