I’m compiling my own catalog of example hide marks as I run across them. So far I’m seeing mostly measurement marks. I have seen a few wrinkled areas, but none that photographed well. Leather Dictionary, on the other hand, has an excellent reference on natural markings.
For measurement marks, if it’s not obvious what it means (e.g. the m2 is a great bet to be square meters), you can lay a measuring tape on the hide and do your own calculations then try a few conversions until you reach one that seems viable.
A hide is marked 139 with each number underlined and this is the first time we’re seeing that mark style. How do we determine what it means?
We measure the hide with a tape and find it to be approximately 3′ x 5′, which is ~15 square feet (sf).
Now we try a few conversions, assisted by Google:
Square Inches (si)? There are 144 si per sf, so 15 x 144 = 2,160 si. Nope, not square inches.
Square Meters (m2)? There are 10.764 sf per m2, so 15 / 10.764 = 1.39 m2. Nope, not square meters but we’re on to something here.
Square Decimeters (dm2)? There are 100 dm2 per m2, so 1.39 / 100 = 139 dm2. Ah ha! Now we can feel pretty confident that this mark style from this manufacturer means square decimeters.
What about other or unknown manufacturers? Do a sanity check with each new source, and if you find the same mark meaning different things, notate those sourcing differences in your catalog of marks.