2c KGV Arch With Strange Features.

I don't have a lot of experience with different paper types but I noticed 'ribs' on this green 2c KGV arch issue and I'm wondering if it could be ribbed paper?

I can even feel the 'ribs'. I notice on the back that it has vertical watermark(?) lines, as well as the strong horizontal 'ribs' visible on the front. I also notice that there's an impression of the stamp's design on the back offset from where the design is on the front. Thoughts?

I contrasted the colour in the image of the front to highlight the horizontal 'ribs'. The image of the back is natural colour.

I'm wondering if the 'ribs' are from ribbed gum, rather than ribbed paper. I've just read that gum was sometimes applied in a ribbed manner to stop mint stamps from curling after gumming. I just saw the same effect on the back of a green 1c KGV arch issue.

Would the vertical watermark lines indicate laid paper? Also, would still appreciate ideas about how an offset impression of the stamp design appeared on the back...

Confirmed my idea about ribbed gum... https://goscf.com/t/37378&SearchTerms=ribbed,gum

Ok, answering my own questions tonight lol. I'm assuming the following, unless somebody kindly corrects me:

• The vertical watermark lines are from wires on a Dandy roller used in the paper-making process


• The offset image on the back was caused by the sheet this particular stamp was taken from being laid onto another sheet before the bottom sheet dried, imparting ink from the bottom stamp's design on the back of this stamp.

In this issue, many of the stamps were printed on a Rotary Press and that is what causes the horizontal lines you see on this stamp. Common on the 1c Green. Of course, it's always possible to find "Arch" Issue stamps on both Flat and Rotary Press. An example would be the 5c.