Check the paper from back under high magnification - the #179 is printed on wove paper and the wove will show clearly under magnification. The #185 is on soft porous paper, if it is a used and soaked example (without hinge or gum remainant) than you can feel the paper softness, under magnification the paper will look different. Better to scan the backs under high resolution than things will stand out more clearly.
Another way to check for wove paper is to hold the stamp up to a strong light and look at the reverse using a good manifying glass. You should be able to determine if the paper has either a vertical or a horizontal mesh, indicating a wove paper. This is easiest on used ungummed stamps.
re: US 179 or 185? Wove vs. soft porous paper
Check the paper from back under high magnification - the #179 is printed on wove paper and the wove will show clearly under magnification. The #185 is on soft porous paper, if it is a used and soaked example (without hinge or gum remainant) than you can feel the paper softness, under magnification the paper will look different. Better to scan the backs under high resolution than things will stand out more clearly.
re: US 179 or 185? Wove vs. soft porous paper
Another way to check for wove paper is to hold the stamp up to a strong light and look at the reverse using a good manifying glass. You should be able to determine if the paper has either a vertical or a horizontal mesh, indicating a wove paper. This is easiest on used ungummed stamps.