..Are you sure it's a duncan? ..Do you have a mutimeter to find out the D.C. Resistance? ..I think "B" stands for 'bridge' & "C" is the first letter of the employee's last name that made the pup? ..Or the "C" could be for "Cool Rails"? ..I don't own any single coil-sized hums yet, so I not the best to answer this question. ..If you could test the DC I'm sure I could help more.