The highest value of the Ruble HH surcharge type is the 100 ruble overprint. Here a stamp with a genuine overprint – in this case a good or even a little overinked example:
Lets have a look at this overprint in more detail, starting with the upper part, the so-called monogram. 
The size of the monogram is smaller in comparison to the 1r, 10r, 25r and 50r overprints. The first angle of the H (part of the monogram) almost touches – or like shown in this example touches the head of the S (part of the monogram) – see the upper arrow. The frame lines of the S are thin (again here overinked, but you can see that it is hollow), but tend to smear together at the end at the base of the H – see lower arrow.
The lower part of the overprint shows even more characteristic signs.
The most striking distinguishing mark of the genuine overprint is that the single characters are not on a single line but especially the second “0” is placed higher. You can instantly weed out anything as fake, were you cant see this uneven placement. If you take a closer look, you see that also the first “0” and the “r” are a bit higher than the “1”. Please also note the tilting of both “0” to the left. The second most important feature of the genuine overprint is the size of the “0”. The second “0” is smaller than the first one. This can be seen very good when you compare the inner horizontal width. The shape of the “1” is similar to the shape on 1r and 10r overprints. Although there is quite some variety to be found. The “r” is thick and quite wide and that is also like with the “r” on 1r and 25r overprints. The spacing is also uneven. Between the “1” and the first “0” is more space than between all other figures.
Quick summary:
- Second “0” clearly above base line
- Inside of second “0” is smaller (horizontal width) then the first “0”
- Both “o” tilt to the left
- Large space between the “1” and the first “0”
- “r” is wide and never closed