Try MIL-22-STD from the Department of Defense Design Criteria Manual for weld joint design.....
B butt joint
2 welded both sides
V bevel or v groove
. period used for separation
3 fourth character is assigned in sequence, 1, 2, 3, etc to cover distinctive joint differences such as bevel, angle, root opening, with backing, without backing, etc.
Try to google MIL-STD-22D-Navy BMR
It's in the "Forward" section, pg 3 of 81