I have several of Roman States stamps that have impressions on the back. Are they just offset ink or are they called double impressions or impressions on both sides?
The 1854 printing of this set used an oil based ink that bled through the paper so that the printed stamp shows through the back of the paper. That's what this looks like to me.
I have several of Roman States stamps that have impressions on the back. Are they just offset ink or are they called double impressions or impressions on both sides? 
