Information incomplete. Under construction.
The 1/4d is one of the more interesting plate layouts of the series.
Both plates were created before issue and both were used contemporaneously for printing. The distinct shades of pale Magenta vs Bright Magenta *might* indicate a boundary in printings between plates.
A standard, narrow, imprint is in the standardised lower left corner of each pane for both plate layouts. This is at odds with most 320on formats where a wide Ash imprint initially appears in the central gutter between panes.
This means that, similar to the 1/-, the intention was to only issue post office sheets as single panes for such a high denomination, creating a need for imprints to make all panes indistinguishable.