George Washington Stamp With Extra Perforation Hole?

hello everyone,i saw this stamp in my album and think it is unusual.there are 13 perforation holes on the left while 12 perforation holes on the right vertical sides.normally are 12 perforation holes on both sides.the top and bottom horizontal holes are 11 which are normal.beside that,the stamp is alittle bit slanding when I put it straight(i mean the picture).i have no idea what caused this happend.please help me if you know something about it.thank you.

I'm not an expert on perferations, but I don't think there is any rule that says there has to be the same number of perfs on both sides of the stamp. If one cutter is slightly off line from the other I can see it happening.

I'm assuming both left and right side perfs are the same size.

Miko....

Use a perf gauge and measure the holes and teeth.