This has probably been talked about before here, but I'm new. I heard that the S in the Model BGS stood for "Studebaker", since they made the engines? for some BGs. This true?
The 'S' suffix does mean Studebaker, as some of the Hercules JXD engines were contracted out and built by Studebaker.
There is also an 'H' suffix for some of the Cletracs (BG included) which stands for Hillside or wide gauge for stability.
Thus, a BGHS would be a Model B Gas engine Hillside model with a Studabaker built Hercules engine.