I suspect that this gun does not have a selective trigger. My past experience with BSS are that the models that are selective have a gold trigger and by the picture does not have the selector on the trigger guard.
The earlier models were not selectable. The one pictured is not, as the selector button would be right behind the trigger. Chokes are generally IC/Mod for 26" bbls and Mod/Full for 28 and 30"--though I've seen exceptions to that. Generally good guns. I've owned three and had no issues.