Back in the '40s I remember yard conductor's marking cut's to be cut
off for each track when they were braking up a train. They would use a
light color chalk and always try to mark the cut in the same spot so the
man making the cut could pick it out of all the other chalk marks. I
saw this in flat switching yard's and hump yard's were the yard was not
completely automated.
I would say the number of chalk mark's per car would depend on were the
car had been , the weather it had passed thru and how often it needed to
be chalked.
Dennis Carpenter