That looks like a Bridgestone from before they introduced the Kabuki brand. In the 1970's there was a craze for Japanese stuff, so they changed their branding because Bridgestone sounded too American. The "BS" stamps probably didn't help either. The "lugs" on your bike are actually aluminum that is cast in place around the frame tubes. That is why the seat post has to have an expander wedge, the lug is too stiff for a normal pinch bolt. They also made one with stainless steel tubes, called the Submariner. Your bike appears to be a higher end model, having cotterles crank, better SunTour deraileurs, and downtube shifters. It is in great shape for something that is 30 years old. I have a Bridgestone-Kabuki Super Speed that has a similar frame, but lesser cranks and deraileurs. It is a nice riding bike, although somwhat heavy. I have converted it to a three-speed and changed to alloy rims, which pared it down to 29 pounds.