Since my original post I have been observing this thread and although some people have offered some speculation about 'user error' or 'try this and try that'. just to confirm, and to rule out speculation:
I know my equipment works to dump the 83850C drives as I got another one (drive manufactured July 2009, Xbox manufactured 2009-08-05, Lot 0932X, Team: FDOU).
That drive dumped all the LO83info just fine. (See first page for info on the one I couldnt dump)
No the 83850C made in August 2009 that I was attempting to dump did not work with any method attempted. first and foremost it did not work with probe, did not work with the original lo83info provided by foundmy.com no it did not work with dosflash16 or dosflash32, jungleflasher old or new, etc...etc...
Yes some people have modded drives manufactured August 2009, however there is every possibility that something has changed internally in the firmware half way through the month.
Jungle flasher reports it as "8385" just like all othe pre-august ones.