4d brown-ochre Pictorial (sideways wmk) with Double Perf

[Ross Ewington]

I just removed this from a small envelope piece found in the remnants of some "junior collections"
I purchased recently, albeit reluctantly.
[attachment=0]q1196.jpg[/attachment]
The stamp is the 1911 4d brown-ochre Pictorial with Crown/A wmk sideways - perf.11 B/W T54C
with double perforation (also perf.11) at top and as such is not listed in the Brusden/White catalog.

Does anyone have another example? I have only ever seen double perforations on the perf.12.4 stamp and
this has not been a particularly regular occurrence.