Den,
my “I-Spy book of Tractions” tells me that the way to spot an 11BL/Light 15 is the “slope” at the top of the front grill when viewed from either side.
If it curves back it’s an 11BL/Light 15, If it’s a straight slope then it’s an 11B or 15/6.
11BL
[attachment=1:16rc2c7y]11Bl.jpg[/attachment:16rc2c7y]
Not an 11BL
[attachment=0:16rc2c7y]not 11 BL.jpg[/attachment:16rc2c7y]