I didn't mean "in series". Bad wording on my part. Really meant two GFCI devices on the same circuit. My understanding is that they can sort of fight with each other, and cause one or the other to trip.
I can see this happening with a homeowner who thinks his kitchen isn't protected and installs a GFCI outlet, when it was actually protected from a GFCI outlet installed in the garage. From reading other posts regarding circuit requirements for kitchens, this sounds like it won't meet code today, but apparently it did at one time. Makes it a pain to find when you trip it.
Methinks that is what you were trying to post, a GFCI followed by a GFCI. Posters on board mention that doing that will cause issues down the road. One of the few things I have yet to stumble across, but then again tomorrow is a new day.