I received my drive yesterday. It's a HP branded ES with FW 4IWTHP09 on it.
My google-fu turned up nothing on that FW, or, for that matter, anything on the particular HP partnumber (804638-001).
Also, it appears that HP is pointing people to using the Intel SSD tools in order to do FW updates and such, which, no matter which version used, reports that firmware is up-to-date.
I'll be doing some testing of the drive later today/tomorrow and see where it stacks up and see what else I can find out (like when it was Mfg'd and such).