what is a b mark on steel

huangyhg

what is a "b" mark on steel?
i am looking at the plans for a steel frame and masonry building from 1964.  several of the beams use a notation as follows:  10 b 11.5.  is that a wide flange section?   
10b11.5 is a light weight rolled section similar in appearance to a wf section.  they appear in the aisc steel handbook of sixth edition and earlier.
the properties are as follows:
depth 9.87"
flange width 3.950"
flange ave thk 0.204"
web thk 0.180"
area 3.39
d/af 12.3
ixx 51.9
sxx 10.5
rx 3.92
iyy 2.01
syy 1.02
ry 0.77
from the reference: iron and steel beams 1873 to 1952 published by aisc, there were many designations given to beams before standard rollings were adopted.  in other words, each steel mill would roll a slightly different shape.  some of the designations follow.
b - bethlehem steel company
c - the carnegie steel company, ltd 1893 - 1896
c - carnegie steel company 1900-1934
ca - cambria steel company
cam - cambria steel company
cil - carnegie-illinois steel corporation
cp - carnegie phipps & co. limited
il - illinois steel company
in - inland steel company
.
.
.
us - united states steel company
the above reference is invaluable for working with older structures as it not only contains properties but also stresses of those mill products.