All stamps – with the exception of the 500 rubles – are reprints. And so it is no surprise, that the overprints are fake. Some are warped and twisted, like the 15 and 20. They cannot stand in comparison the genuine overprints. See the two “5” overprints. The hollow “4” is one of the most common fake overprints found on the 100 rubles stamp.
Here two stamps – one original printing with genuine overprint and one of the reprints with the hollow “4” fake overprint.
The overprints in detail.
Here a stamp with a genuine 20 overprint.
The overprints in detail.