Mine were a mix. Most were T4 (though the T3 bit works, with the risk of rounding off the screw). The screw by the volume buttons was definitely a T3 though. The two by the USB jack might have been T3 or T4, couldn’t tell.

From the photo it looks like the big chip on back is marked "8443 ARN", not "8443 ARM" ... I'd guess that it's the Flash, and the (much smaller) chip on the other side is the (probably ARM-based) controller.