

I have checked other sites and here are some examples:
Link 1
Link 2
Link 3
And if I compare them with another 20 kopek around the same era,

I hope you can see that the die size of the obverse seems to be awfully small.
I was thinking that it might be a die meant for a 15 kopek was accidently reengraved as a 20 kopek, but my theory was thrown out of the window as the inner diameter of the 1907 20 kopeks that I got measured 1.9mm against a typical 15 kopek 1.8mm (if I got them right...)
Any possible explaination of what is going on?