Hey Wert, sorry to pop your bubble, I believe the 260 Salmon stamp is not an offset, but more of a thin type paper. Most offsets occur when the printed side of the sheet is placed under the gum side of the sheet above during printing. Basically the ink transfers to the gum.
As for the 262 Seal stamp, I believe that is some type of Aniline ink that has seeped through. I also have a copy of that. See my attached photos and other goodies.
they are
255 Reverse offset Red 3c
261 Pelure paper, showing design from back of stamp Black Dog 14c
262 A Copy of the Aniline ink type you are showing 15c rose violet
262i Reverse offset with pre printing crease 15c rose violet
263 Reverse offset 20c green
269 Reverse offset 4c blue
Cheers
Trodent





