If you collect tough backs long enough you will realize there are subjects that are tougher in each brand. The rarer the back the harder this is to see.
Example Red Hindu Murphy is much tougher than Red Hindu Ford.
Same with black Lenox, M. Brown, Cobb and Konetchey are much tougher than Ames or some of the Giant portraits with sweater which show up much more with black Lenox.
As for Cairo and brown Lenox, these are two completely different ink colors
