Technically two, as mine has the missing bits a bit to the right of the other.
Not that it matters, It's a interesting variety that probably reflects a different place on the plate, but I wouldn't consider it as a major one.
(Neither are Nodgrass, dopner etc.)
Of course if everyone chooses to call it a variation and place a nice premium on it I won't mind a bit
Another possibility is actually a damaged plate. It would have to be a pretty deep chip to not print anywhere. I wouldn't mind seeing the Ebay one up close. If the missing area starts at the same spot and the r has the same deformed look I might start thinking it was a chipped stone that got worse over time. It would be a print defect rather than variation, but a more interesting one.
Steve B