These are inverted versions of relatively uncommon fiscal perfins of North Borneo. They do not show up that well with an ordinary scan. With background illumination and photography, the details are clearly evident. The photos were taken using a Samsung Galaxy phone.
Scanned version of a inverted "Judicial" perfin.
Photo taken by placing stamp on lamp shade and then edited accordingly with photoshop.
This is with background daylight suspended in a transparency.
Scanned version of a inverted "Revenue" perfin.
With lamp shade in the background.
With a background of natural daylight.