I can't remember the name, but no the cylinder was made buy another company. If I remember correctly the I-I cylinder was made by inland. Yes, BLC was a GM division. I am not sure if BLC made the complete barrels with the cylinder installed or if the shipped they to inland without the cylinder and inland installed them.
If someone does not jump in before I will get you some info and pics of the difference between the BLC and inland barrels
Dave