Early Quad II With Giant Power Xformer?

Hi all- I pickup up an earlier Quad II (serial no 2331, can't verify that this is the original plate) that has a HUGE power transformer. It is about 1.5 times higher than the standard Quad II, a bit wider (although the chassis measurements are standard), and weighs a ton. The rest of the chassis of the amp looks like standard Quad. I've done some googling and forum searching, and have been unable to find any info on this amp. Anyone every seen one like this before? Is this actually a Quad or a knockoff or...?

Thanks,
Mike