Vat Dyed Leather

Vat dyed is just like it sounds, the tanned leather is allowed to soak
in vats with vegetable dyes and then polished.  The advantage over a
pigment finish is that there is more depth to the dye. The exterior look
can be more or less shiny.  The main difference between a vegetable dye
and milled or drum dyed cowhides will be the feel, the vegetable tan
will be much firmer, especially when new.  The bags will, of course,
soften when used.

Derek Alexander categories that use vegetable
tanned cowhide are:

Valencia (VA) and Yukon (YK)