Got my first single Friday (shipped 8/22) and it's marked "BitFORCE - 1.0   Rev: E" with big fan & copper tubed heatsink on top, and smaller fan & heatsink on bottom.  Oddly, it shipped with 872 firmware but would throttle error every minute or so.  Took half the case off, propped it up a little higher and it's fairly stable now with 832mh firmware.  

Watching the temps in Cgminer, I've not seen it go over 48.2C.  Anything higher seems to trigger throttling on mine (which stops the temp reads for 15 seconds).  Temperature appears to cycle up & down half a degree or so.  Do you suppose Cgminer is cycling back & forth reading each of the two chips?

I see there's a lot of variation in these singles - some hash high at low temps and some hash low at high temps with others in between.  It would appear the overheat/throttle trigger temp is variable and built-in to the chip.  In other words, luck of the draw.