The lilac overprints of the HH (ruble) overprints are much rarer then the black ones. In order to get a feeling for the look of the genuine ink you need several items with this overprint, the more the better. This is quite a challenge to do with the lilac ones. That the lilac ink was not as suited for overprinting as the back ink, makes it not better.
This item is especially nice because it features a black overprint and an lilac overprint. That the overprint is inverted is not as rare, it actually happens quite often.