We use chrome-tanned leather because it tends to be more supple and more pliable than vegetable-tanned leather. It also has higher thermal stability and does not discolor or lose shape easily.
Common leather markings, such as vein marks and brands, are all part of the unique look that defined leather. If you are look for “perfect” unmarked leather then you are looking for something that has been overly treated and not as true to the hide. Also, colors may vary due to differences in dye lots.