ok here's a bit more info i found out
all info from the same book
field experience brought several suggestions for modifications from the troops in the field and these were incorporated in the Ausf A, 1,768 of which were manufactured. This had thicker turret armour strengthened suspension and ball mounted machine gun instead of a letterbox flap in the glicis plate, while episcopes replaced the direct vision slits in the commanders cupola. As a result of these modifications overall weight inevitebly went up. On the final model the Ausf G which went into production in March 1944 further improvements were made to the transmission, the drivers vision slit was replaced by an episcope and extra armour was added to the upper hull sides to give greater protection to the fuel tanks. Ammunition storage was increased from 79 to 82 rounds. 3,740 Ausf Gs were manufactured before the wars end.