According to Encyclopedia of German Tanks of World War Two by Chamberlain and Doyle
" The Ausf B was the 2nd and 3rd Series of the StuG, differing from the previous model by improvements in the drivetrain... Some of the 2nd series of the Ausf B production had a new six-spoke drive sprocket, and an eight-spoke idler,...by the end of 1940, the number of Sturmartillerie batteries had been raise to seven, and four assualt-artillery detachments,...Additional assault-artillery attachments equipped with Ausf B were formed early in 1941. Two Sturmartillerie Abteilung were present in the Balkans campaign and six Abteilung advanced into Russian territoy in June 1941."
Given that there were 30 StuG A's made by the end of May 40', 320 StuG B's made by the end of May 41', and that only some (number unknown) of the 2nd Series of the StuG B received the new six-spoked drive sprocket and eight-spoked idler, I can only guess the the slim majority of all StuG B's would have the new drive-sprocket and idler, this is based on the assumption that the each series had an equal number of StuG's produced. Given that the production of the Stug B's was from June 1940 - May 1941 and the previous information I would hazard a guess that there is a strong, but arguable, conclusion that the StuG B's, for your question, had the new six-spoked drive-sprocket and new eight-spoked idler.
Sincerely,
Kromyr
[ July 09, 2004, 10:28 AM: Message edited by: Kromyr ]