FROM cfrphoto on 4-20-2018: I did a cursory check of some 3 cent Scott 158 stamps in the reference collection and found that vertical rib paper examples are taller and narrower than examples with horizontal ribbing. I also checked a few US official examples and found the same relationship between vertically ribbed and special printings with horizontal ribbing. I did not check plain examples to determine if two size populations exist. The Scott Catalog reports that National grilled stamps in the early state tend to be taller, printed on vertical mesh paper, and examples with late state grills, printed on horizontal mesh paper, were shorter, with a height difference of about 1/4mm.
On the heels of cfrphoto's post I'm resurrecting this thread to ask a related question pertaining to Palestine Mandate stamps:
a certain stamp series (the pictorials) was partially produced on what the catalogues call "vertically ribbed paper" and also "thin semi-transparent vertically ribbed paper". These are generally considered 2 different paper types - but I'm wondering if this may be the same type of paper in both cases.
From what I've read the ribbing process (done in the UK along with the stamp production) was accomplished by a machine during the drying process after the paper had been gummed:
If the ribbing on the thin paper is light and not very pronounced like on the regular thicker paper issue, is it possible that this is the reason why one version is on thinner paper and another on thicker paper - that the paper thickness is the result of how pronounced the ribbing is, how bunched up the paper has become, and not actually a different type of paper?
As I read cfrphoto's post above a similar thought ran through my head: a horizontally ribbed stamp may be shorter than a vertically ribbed stamp purely because of the tension in the paper pulling it in and making it shrink (and not because of a different type of paper being used)? And likewise a vertically ribbed stamp may be narrower because of the paper being pulled from the horizontal axes?