The Roy Building has now been reduced to two stories.
The window detail is now clearly visible from the top four floors. It appears that these are the ghostly remnants of the Roy's original windows. I can only assume that the Roy's windows were framed into the top two floors in 1928, before the plans for the Eaton's building were known. Or the contractor built the floors with windows because that's what the plans called for, dammit, even though they already knew Eaton's would catch up and cover them.
I zoomed in pretty closely on my original photos and it seems clear the brickwork in the window areas is quite consistent with the rest of the wall and was installed at the same time. It seems to me that the Eaton's brick was laid (from the inside of course) against the wall of the older Roy Building, and the bricklayers simply cut in around the windows and sills of the Roy building, hence the gaps under each window.
As was visible in the previous photos, the Roy contractors just left the glass in place in the covered-over windows in some cases, while in others it appears the windows were removed and replaced with plywood or plasterboard. Presumably this helps explain the different levels of discolouration.
An interesting snapshot from the past, which will soon enough be covered up again.