My guess is that it could be the original head. The date you see is when the head was cast. After that, it went for maching of the valve seats, head gasket surface and so on. Then, it went for assembly of the valves, and all the related things. Between the different operations, the head was probably stored at different shelves or in storage rooms. The operator that was to machine a head wouldn't care what the date code was, has probably grabbed the nearest part and put it in the machine.

Since the date codes are only a couple of weeks apart, I would assume it is the original head to that engine.