Help Me On This China Old Stamp Please, Possible Error?

Hi,nice to see you again,this is a pair of reaper stamps of china issued in 1915-1926.I can notice there is a missing perforation hole on top left vertical side,now the perforation holes are 16 holes instead of 17 holes normally on the center and right vertical sides,the top left corner is in round shape.Is this common on any other of china reaper stamp?Possible error?Please give me your opinion and advice.Thanks for your help.

Nothing unusual for these stamps.They were all line perforated.In the corner spot upper left
there should be a corner piece.Line perforating was irregular and the perforations did not
align themselves;especially in the corners.Another example below: