Numbers perforated in Russia 5 ruble 1909, why?

I have only quesses, but who would know why there are these numbers perforated:


http://aijaa.com/0004810375358

(sorry, poor mobile phone pic)

 

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Here's a link that might help. I'm at work so I can't go through the list myself.

http://www.atsnotes.com/banknotes/russia.html

 

Thanks - very informative link! It seems to be North Russian civil war perforation "GBSO". I have to get that Pick book for more information.