I agree with jimjung, long coronation has multiple re-entries, perforation varieties and more than likely multiple re-touched frame lines. I guess this stamp was as studied as the 1c, 3c or 7c of the series.
My copies 20 copies of the 20c have various top frame thicknesses or straightness/waviness.
here is some of my copies for comparison
RIGHT CORNER BLOCK

LEFT MARGIN BLOCK

While we are looking at varieties, Does anyone have one like this?
Extended E in Newfoundland

Close up

Extended Frame line Upper Left

Trodent